Unit 1: Periodic Motion Lesson 1: osciLLatory Motion Lesson 2: Wave motion

Lesson 1: Oscillatory Motion Types of motion: 1.

Transitional motion

changes the initial position of the object. An example is

the motion of the car on the road. 2.

Periodic motion

is regularly repeated in equal periods of time.

1

An example is the motion of the pendulum & water waves. Motion

Periodic Motion

Transitional Motion

Ex. The motion

Oscillatory

Wave

Motion

Motion

of a car Ex. Pendulum

Ex. Water waves

Activity 1  Aim: To define oscillatory motion. 

Tools: A pencil , a 30 cm long thread & a quarter pound coin.

Steps

1.

Tie the coin with one end of the string & tie the other end of the thread around the middle of the pencil to setup a simple pendulum.

2.

Hold the pencil with your left hand, and pull the coin to the right. Then, let it go according to the figure.

 Observation

2

The oscillating body (The coin) moves forward & backward. ď&#x192;&#x2DC;

Conclusion

1. The coin oscillates around a point of rest (equilibrium) where the velocity &

kinetic energy of the coin is maximum just before it reaches the point of rest (A). 2. As the coin moves away from the equilibrium point , its velocity & kinetic energy decrease.

Oscillatory motion Tuning fork

Swing

Circular motion Rotary bee

Stretched string

The Microwave oven Microwaves cause the vibration of water molecules inside food . Water molecules collide with each other producing a lot of heat energy

to coo

the food faster. Pots made of pottery , ceramics or glass are used in the microwave. M etal cooking pots arenâ&#x20AC;&#x2122;t used inside a microwave because metal reflects the microwaves bac to the source.

3

Microwave oven

Activity 2: 

Aim: To represent oscillatory motion by a graph

Tools : Smooth paper tape winding around two rolls – weight – nail– spring–pencil.

Oscillation of a pendulum

Steps: Use these tools to set the following apparatus.

Pull the spring downwards then let it go. While winding the paper roll regularly.

Observation:

The graph represents simple harmonic motion (oscillatory motion).

Properties of oscillatory motion 1. The Amplitude is the maximum displacement achieved by an oscillating body away

from its point of rest. It is measured in meter (m). 2- The complete oscillation is the

movement made by the oscillating body when it passes a single point in its path of motion, two

consecutive times in the same direction. The pendulum completes one oscillation when it covers the distance:

B-A-C-A-B

A complete

oscillation consists of 4 amplitudes.(4 displacements) Amplitude

4

C Amplitude

The periodic time is the time needed by an oscillating body to make a complete oscillation The periodic time is denoted by (T).Periodic time is measured in seconds (s), andis determined by the relation:

Time (s)

Time= APeriodic solved example: What is the periodic time for the pendulum oscillating in the figure?

No.time of complete Periodic = Â˝ x4 oscillations =2s

Frequency (F) is the number of complete oscillations in one second. The unit of frequency is Hertz (Hz). A simple pendulum makes 50 complete oscillations in 10 seconds, its frequency is 5 Hertz. Frequency is the reciprocal of the periodic time.

Frequency =

1

No. of complete vibrations

Frequency =

Time (s)

Periodic Time

Solved exercise An oscillating body makes 120 complete oscillations in one minute. periodic time and frequency & periodic time. F = 120 complete oscillations Ăˇ 60 s = 2 Hz T = 1/F

5

Calculate the

=1/2 =Â˝s

Multiples of the hertz 1 kilohertz = 1000 hertz 1 Megahertz = 1x 106 hertz 1 Gigahertz = 1 x 109

[1] â&#x20AC;&#x201C;Complete the following: 1. The complete oscillation includes --------------successive displacements, each of them is called ------. 2.In microwave ovens, the oscillating molecules of ----present in food vibrate by the effect of --------. 3. The unit of measuring the frequency is -----------, while the unit of measuring the periodic time is ------. 4. The ----------- is the maximum displacement done by the oscillating body away from its ----------- position.

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5. The -----------& ---------- motion are two types of periodic motion.

Q2. Write the scientific term: 1.The periodic motion made by a body around its point of rest, where the motion repeated through equal interval of time. ( -------------------) 2.The time taken by the oscillating body to make one complete oscillation.

(---------------------)

3.The number of complete oscillations produced by the oscillating body in one second. (---------------------)

Q3. Give reasons: 1.The oscillatory motion is considered as a periodic motion. ------------------------------------------------------------------------------------------------------2.Metallic pots are not used in microwave ovens. ---------------------------------------------------------------------------------------------

Q4. Choose the correct answer: 1.

The result of multiplying the frequency of an oscillating body

7

by its periodic time equals ------------------. (Variable value-Negative value -Constant value- ones) 2.In the opposite figure, when the ball of the pendulum moves from [x] to [y] in a duration of 0.02 seconds, the frequency equals ------------Hz. (0.04 – 0.02 – 25 – 50) Y

X

3. If the frequency of an oscillating body is 6 Hz, so the periodic time is ------------. (3

sec. – 6 sec. – 1/3 sec. – 1/6 sec)

4.The following figures describe the oscillation of a simple pendulum at different intervals of time. The amplitude of such pendulum= ------------------cm. (30 – 25 – 20 -10)

10cm.

20 cm.

30 cm.

8

25 cm.

[5] What is meant by: 1. The time taken by a spring to make 60 complete oscillations is 1 minute. ------------------------------------------------------------------------------------------------------. 2. The number of complete oscillations made by an oscillating body in 10 sec. is 500 complete oscillations. ------------------------------------------------------------------------------------------------------.

Lesson 2: Wave motion

A drop of water that falls on the surface of still water causes

the propagation

of concentric circles on the surface of water &

Represents wave motion.

The role of waves in energy transfer Activity 1 Place the dominos in the form of a line at equal distances from each other. Push the first domino. ď&#x192;&#x2DC;

Observation:

â&#x20AC;˘ The pieces fall consecutively.

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• The first domino piece falls transferring its energy to the next one. The 2nd

piece falls down in turn transferring the energy to the next piece and so on. •

Energy transfer through the domino pieces continues and the pieces never change position in the line.

Conclusion

The disturbance that propagates and

transfers energy in

the direction of propagation is known as a

wave.

When you push coin (x) towards the groups of coins , coin (y) moves. The energy

of coin (x) is transferred to the other coins then coin (y) causing its motion.

Activity 2:  Aim: To conclude the concept of wave motion 

Tools: A hollow tube 30 com long, a burning scent stick.

a candle, a tuning fork.

Steps:

 Place the tube horizontally and place the candle at one of its ends and the scent

stick at the other end.  Hit the tuning fork and place it near the scent stick. 

Observations: The flame of the candle vibrates.

Conclusion:

Sound energy causes the vibration of the air & smoke molecules. The energy is transferred to the flame.

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Wave motion is the movement that results from the vibration of the particles of the medium in a specific direction.

The direction of the progress of the wave is the line of wave propagation

According to the direction of vibration of the particles of the medium , waves are classified to transverse & longitudinal waves. Activity 3:

 Aims: To compare transverse waves & longitudinal waves. 

Tools: Spring , coloured tape & a nail.

Steps: a. Fix one end of the spring to a wall using the nail. b. Tie the colored tape at the middle of the spring.

1

case: Move the coil up & down perpendicular to the axis of the spring.

Observation1: The rings move up taking the shape of a crest then the rings move down taking the shape

st

of a trough.

2nd case Push the coils of the spring towards the wall. 

Observation 2:

the direction of wave propagation (rings of the spring coil) is the same direction of vibration of the medium particles (the colored tape). 

Conclusion

1. The transverse wave is formed of crests and troughs as compared to the

longitudinal waves which are formed of compressions and rarefactions. 2. The highest point in a transverse wave with respect to the horizontal line is

called the crest , while the lowest point is called the trough .

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3. In longitudinal waves, the point of highest density and pressure is called compression, while the point of lowest density and pressure is called rarefaction.

Definition

Compositio n Examples

The disturbance which causes the particles of the medium to vibrate perpendicular to the direction ofwave propagation. It consists of crests & troughs

the disturbance that causes the particles of the medium to vibrate along the direction of wave propagation

Water waves

Sound waves

It consists of compressions & rarefactions

4. During wave propagation, the particles of the medium do not change position;

however they vibrate around their points of rest.

Comparison between transverse and longitudinal waves.

Physiotherapy tubs (Jacuzzi) 12

Jacuzzi is a tub where water moves in circular waves. It's used to treat sprains and cramps when filled with hot water and nervous tension when filled with cold water. It’s found in health clubs.

We can't hear the sound of solar explosions because sound is transferred in the form of mechanical waves which aren’t transmitted through space. We can see the light coming out of the sun which is transmitted as electromagnetic waves that can travel through space. Thunder occurs with lightning at the same time but we hear thunder after seeing lightning because the speed of light is bigger than the speed of sound.

Mechanical and electromagnetic waves: Waves are also classified according to the ability to propagate and transfer energy, into: • Mechanical waves.

• Electromagnetic waves.

Water waves

Comparison

between

mecha nical

electromagnetic waves.

13

waves

and

Mechanical waves

They need a material medium to propagate. Transverse water waves and sound longitudinal waves are

Electromagnetic waves

They do not need a medium to propagate through as they can propagate through space. Light waves and radio waves used in radars are electromagnetic waves. They are all transverse waves.

mechanical waves.

â&#x20AC;˘

Both mechanical and electromagnetic waves propagate in different material media, however the velocity of mechanical waves is much slower than that of electromagnetic waves. Electromagnetic waves propagate in space with a

velocity of 3 x 108 m/s. â&#x20AC;˘ Oscillatory motion is similar to wave motion whether

transverse or longitudinal as each can be represented as shown in the

The following terms

figure.

are also used to describe wave 14

motion : 1. Wavelength 3. Wave velocity

2. Amplitude

4. Frequency

P.O.C.

wave length(位) of longitudinal waves

wave length(位) of transverse waves

the distance between the the distance between the centers Definition of two consecutive compressions or centers of two consecutive rarefactions crests or troughs

1.

The wave

length

The unit of wave length

is

the meter (m) or

fractions of a meter. Millimeter (mm) = 1 x 103 meter Micrometer = 1 x 106 meter Nanometer = 1 x 109 meter

2. The amplitude is the maximum displacement achieved by the particles of the

medium away from their points of rest. 3. The wave velocity is the distance covered by the wave in 1 second The velocity of a wave is calculated by the relation

Velocity (V) = Distance covered by the wave (m)

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Time (s)

The measuring unit of wave velocity is m/s The velocity of sound is constant for the medium . Sound travels with different velocities in different media.

Sound speeds in different media In air 340 m/s

Velocity of sound 4.Frequency

In water 1500 m/s

In wood 1850 m/s

is no. of complete waves covered in a second.

T=1 F The law of wave propagation is a relation between the wave velocity (v) , frequency (F) & wave length ( 位). Wave velocity = Frequency x wavelength V

=

F

x

A solved exercise Calculate the wavelength in meter for a visible light wave of frequency 6 x 108 Megahertz & velocity 3 x 108 m/s. Frequency = 6 x 108 x106 = 6 x1014 Hertz Wavelength =V梅 F = 3 x 108 梅 6 x1014 = 0.5 x 10-6 meter. Can you compare between the oscillatory motion and the wave motion?

Electromagnetic Pollution Mobile phones use electromagnetic radiation in the microwave range & some believe this may be harmful to human health.

16

Therefore scientists are doing research to confirm or deny the health hazards of mobile phones & transmission stations.

[1] â&#x20AC;&#x201C; Complete the following: 1. Waves are classified according to the ability to propagate& transfer energy into ------------waves& -----------waves. 2. Radio waves are considered ---------- waves that propagate through free space with a velocity of -----------. 3. The transverse waves are formed of -----------& -------while the longitudinal waves are formed of -------& --------. 4. The crest in the ----------- wave is equivalent to the ------------ in the longitudinal wave. 5. Wave velocity = ------------x--------------. 17

[2] Write the scientific term: 1. A disturbance that propagates& transfers energy along the direction of propagation.

(---------------------)

2. The waves which need a medium to propagate. (---------------------) 3.The distance between two successive crests or troughs. (---------------------) 4.The distance that is covered by the wave in one second. (---------------------) 5. The area in longitudinal wave at which the particles of medium are away from each other. (-------------------)

[3] Correct the underlined words: 1. The movement of the clock pendulum is an example of wave motion. 2. Light waves& sound waves are examples of electromagnetic waves. 3. The transverse wave is a disturbance in which the particles of the medium vibrate along the direction of wave propagation. 4. A body of frequency 200 Hz makes one complete wave in 200 seconds.

[4] Give reasons: 18

1. The waves produced due to vibration of a string are transverse mechanical waves. ---------------------------------------------------------------------------------------------------. 2. We see lightning before hearing thunder. ----------------------------------------------------------------------------------------------------.

[5]. Choose the correct answer: 1. Jacuzzi is a tube where water moves in the form of -----waves. (circular – longitudinal – oval – non of them) 2.If the distance between the center of the third compression & that of the fifth compression on the wave propagation is 20 cm. so the wave length of this wave is-----------------. (40cm – 20 cm – 10cm – 5cm)

6. What is meant by: 1. Wave length of a sound wave is 30 cm.

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-------------------------------------------------------------------------------------------------. 2. The distance that is covered by a visible light waves in two seconds is 6 x 108 m. -------------------------------------------------------------------------------------------------.

7. What happens when: 1. The particles of the medium vibrate in a direction normal [perpendicular] to the direction of wave propagation. --------------------------------------------------. 2. The frequency of a wave is doubled [concerning the wavelength] when the wave velocity is constant. -------------------------------------------------3. The frequency& velocity of wave propagation decreases to quarter. (Concerning to the wavelength) --------------------------------------------------.

8. Cross the odd word out, then state the relation between the remaining: 1. Sound wave – Light wave – Radio wave – Infrared wave. --------------------------------------------------. 20

2. Pendulum's motion â&#x20AC;&#x201C; spring motion â&#x20AC;&#x201C; rotator bee motion stretched spring motion. --------------------------------------------------.

9. From the figure, find: a. Wavelength b. Frequency

Disp (m)1

4m

c. Amplitude

tim (s)

d. Wave velocity

2s -1

10. Problem: Sound waves of frequency 200 Hz& wavelength 1.7 meters. Calculate: a. The velocity of sound waves propagation in air. b.The wavelength of these waves of frequency 200 Hz when the propagation in water with velocity 1500m/sec.

Solution

21

11. Mention the use of: a. Jacuzzi. -------------------------------------------------------------------------------------------------. b.Radio waves. --------------------------------------------------------------------------------------------------.

Unit 2: Sound & light Lesson 1: Properties of sound Lesson 2: Reflection of sound waves 22

Lesson 3: The wave nature of light Lesson 4: Reflection & refraction of light

Lesson 1: Properties of sound Sound is an external stimulus that affects the ear and causes hearing. 1. Sound is produced by the vibration of the bodies. 2. Sound waves are mechanical longitudinal waves that travel in different media in the form of spheres, where the center of these spheres is the source of sound.

3. The velocity of sound in air is 340 m/s

Solved Questions: a. Whatâ&#x20AC;&#x2122;s meant by : the wavelength of a sound wave is 1.5 m ? Answer: the distance between the centers of two consecutive compressions or rarefactions is 1.5 m b. Calculate the wavelength of a sound wave propagating(traveling) in sea water with velocity 1500 m/s , the frequency of the wave is 10 kiloHertz

10 kiloHertz = 10x 1000 = 10,10 Hertz Wavelength =

Wave velocity 23

Frequency Wavelength = 1500

10,000 = 0.0015 m

Sounds heard by the human ear are classified into two types: Musical tones

P.O.C.

Noise

1-

Frequency

uniform frequency

non-uniform frequency

2-

Effect on the ear

comfortable

uncomfortable

3-

Source

violin

drill

The ears distinguish different sounds because sounds differ in 3 characterisitics: Sound pitch. Sound intensity.

First: Sound Pitch Sound quality.

The sound of the lion is

harsh & that of the sparrow is high.

The voice of the woman is sharp or high-pitched compared to a man’s voice which is low-pitched. 

Activity 1:

Aim: To conclude the relation between frequency & the pitch of sound.

Tools: Big book –

rubber band – 2 pencils

24

Steps:

1. Tie the rubber band around the book . 2. Insert the two pens below the band, closer to the book edges. 3. Put your left forefinger on the band at a distance 10 cm from one of the two

pens. 4. Pluck that segment by the forefinger of the right hand. 5. Change the length of the rubber band with your left forefinger then repeat

step 4 . 

Observations

The sound pitch changes as the length of the vibrating segment changes. By increasing the length of the rubber band , the sound pitch becomes sharper (low) .

Conclusion:

1. Sound pitch is a property of sound that distinguishes between harsh and sharp

voices. 2. The sharpness of sound increases as the frequency of the source increases.

 Activity

2: Set up 3 test tubes filled to different levels with

tube & hear the sounds.

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water. Blow across the mouth of each test

Observation: The short column of air gives a high-pitched (sharp) sound. The long column of air gives a low – pitched (harsh) sound.

Conclusion: The vibration of the air molecules above water produces sound. The pitch changes according to the length of air column.

 Activity

3 :Determining the pitch of a tone using Savart's wheel.

I.

Savart's wheel is used to determine the frequency of a tone.

Steps:

1. Listen to the tone for a while. 2. Rotate Savart's wheel at different speeds. The gear is in contact with a

flexible metal sheet. 3. When you hear a tone similar to the first tone you want to find its frequency ,

count the number of cycles taking place in a certain period of time (t). 4. You also need to know the number of teeth of the gear (n) Frequency (F) = no. of cycles (d) x no. of teeth (n) Time (t)

A solved example: What’s the frequency of a tone produced by Savart's Wheel that rotates with velocity of 900 cycles in 3 minutes, the number of teeth of the gear is 30 teeth. t = 3 x 60 = 180 s F = 900 x 30 180 F = 150 Hz 2. Sound intensity

Sound intensity is a property of sound that distinguishes strong and weak sounds (loud & quite). a. The sound intensity at a point is the amount of sound

energy falling

perpendicular on a unit area surrounding this point in one second. b.

Sound intensity is measured by Watt/meter2

26

c. Noise intensity is expressed by Decibel scale.  

Activity 4: Aim: To conclude the relation between the distance between the sound source and the ear & the intensity of sound.

Steps:

At which position is the sound intensity the highest? 

Observation:

The voice is loudest when you are the nearest to the other person. 

Conclusion :

Sound intensity decreases gradually as the distance between the sound source and the ear increases. Sound intensity at a point is inversely proportional to

the square of the distance

between the source of sound and that point.

Activity 5:

Aim: To determine the effect of the amplitude of the sound source on the sound intensity.

Steps:

1. Fix one end of a ruler on the edge of a table by your right hand. 2. Pull the other end of the ruler by the other hand, and then set it free. 

Observation :

The amplitude of the vibrating ruler & the sound intensity decrease by time. 

Conclusion: 27

Sound intensity is directly proportional to the square of the amplitude of

vibration of the source. The figure represents two sound waves A & B. Wave

B has higher amplitude & therefore it’s louder.

B

A

Activity 6 :

Aim: To conclude the effect of a resonating box on the sound intensity.

Tools: 2 mobile phones – a cardboard box with an opening at one end that can fit the mobile.

Steps:

1. Let a mate carry a cell phone (A) adjusted to the vibration mode. Use another

mobile to phone mobile (A). 2. Make an opening at one end of a box , then put mobile (A) at the open end. The

box is a resonance box. Now phone mobile(A) 3. Compare th e sound intensity in both cases . 

Observation:

The sound of the mobile on the resonance box is louder. 

Conclusion:

When the source of sound touches a resonance box ,th e air in the box vibrates increasing the sound intensity.

28

Activity 7:

Aim: To identify the effect of the density of the medium on sound intensity.

Tools:

Air vacuum pump – glass jar – an alarm clock

Steps:

1.

Put the alarm clock on the air vacuum pump

and cover it by the glass jar . Listen to the ring of the alarm clock. 2.

Pump the air outside the jar partially.

Compare the sound intensity before and after the evacuation of air .

Observation:

The sound is weaker after pumping the air out. 

Conclusion:

Sound intensity is affected by the density of the medium that transmits the sound. Sound intensity increases as the density of the medium increases.

Wind direction: Sounds traveling in the direction of the wind are louder than sounds that travel against wind direction.

Factors affecting sound intensity: The distance between the sound source and the ear. The amplitude of the sound source. The area of the vibrating surface (a resonating box). The density of the medium through which sound travels. Direction of the wind. 29 and the ear: The distance between the source of sound

Ear plugs made of silicon are placed in the external ear canal to reduce noise. Why are ears able to distinguish between the musical tones produced by a violin and a piano even if the tones have the same pitch and intensity?

The fundamental tone is a simple tone produced from a vibrating tuning fork. The tones produced from an instrument is a series of harmonic tones that differ in intensity & pitch.

Harmonic tones of different instruments are different & help the ear recognize the source of sound.

Ultrasonic & infrasonic waves: Humans are unable to hear all sounds. An example is the sounds

produced by dolphins because the human ears

are affected by sounds of a frequency range between 20 Hz - 20 KHz

According to th e

frequency range heard by humans,

sound waves are classified into: Infrasonic waves

Ultrasonic

between 20 Hz - 20

waves More than 20 KHz

Sounds produced

KHz heard by the Sounds

Sounds produced

before rainfall

human ear

by bats & dolphins

Frequency less than 20 Hz Example

Sonic waves

30

Ultrasonic waves are used in medical, industrial and military fields such as: a. Breaking down kidney and ureter stones without surgery. b. Diagnosis of prostate cancer. c. Sterilize milk by killing some types of bacteria and stop the action of some viruses. d. Finding land mines.

Ultrasonic cleaner

31

Breaking down kidney stones with ultrasound

[1] –

Complete

the following: 1. The measuring unit of sound intensity is ------------, while that of noise intensity is ---------------. 3. Sound intensity at a certain point is ---------- proportional to the square of the distance between this point& sound source, and is -------------proportional to the square of the amplitude.

[2] Choose the correct answer: 1. Sound wave that propagates through air with velocity 330 m/sec and of wavelength 0.1 meter, its frequency equals --------. ( 330 Kilo Hertz – 3300 Hertz – 33 Kilo Hertz – 330 Hertz) 2.The sound of frequency 200 Hz is --------than the sound of frequency 100 Hz. ( stronger – sharper – weaker – harsher) 3.All of the following are factors affecting sound intensity 32

except ---------------. ( amplitude of vibration – medium density – frequency – wind direction)

4. The human ear can hear sounds of frequency ----------. ( 50 K Hz – 30 KHz – 300 Hz – 10 Hz)

[3] Write the scientific term: 1. Sound waves of frequencies less than 20 Hertz. --------2. An instrument that is used in to determine the frequency of unknown sound tone. ----------------3. The tones that associate the fundamental tones, they are lower in intensity& higher in pitch and different from one instrument to another.-------------------

[4] Give reasons: 1. Sound can be heard from all surrounding directions. -----------------------------------------------------. 2. The difference in frequency between the tone& noise. -----------------------------------------------------. 3.The strings of a musical lute are fixed on a hollow wooden box.

33

4. Sound travelling in air has less intensity than travelling in carbon dioxide. ------------------------------------------------------------------------------------------------------. 5. Piano's sound differs from that of violin even if they have the same intensity& pitch. ------------------------------------------------------. 6. The use of ultrasonic waves in milk sterilization. ------------------------------------------------------.

[5] Using the following figure, compare from the point of view of sound intensity& pitch:

A

B

[6] Savart's wheel rotates with a rate of 300 cycles per minutes. A sound of frequency 600Hz is produced when an elastic plate touches the teeth of one gear. Calculate the number of gear's teeth. ------------------------------------------------------.

34

Lesson 2:

Reflection of sound waves • Sound waves are reflected when they fall on a reflecting surface.

Sound reflection explains: • why the roofs of worship places are built in the

form of domes. • why the ears of the gazelle are big. • how a doctor examines an embryo in the womb.

20 week ultrasound picture

The laws of sound reflection. 

Activity 1

Aims: Verifying the laws of sound reflection.

Tools: wooden plate – foam plate – table – two cardboard tubes, one of them contains a stopwatch

Steps

1. Arrange the tools according to the figure. 2. Fix tube (b) and change the position of tube

(a) until you hear the clearest sound. 3. Change the angle tube b makes with the foam plate then repeat step 2 . 35

Observations

1. You hear the sound clearly when the angle betw een tube (a) & the foam plate =

the angle between tube (b) & the foam plate. 2. The sound isn’t heard clearly when tube (b) is perpendicular to the table.

The following figure represents a sound ray (a) , the reflecting surface & the reflected sound ray

Conclusion

The laws of sound reflection are : The angle of incidence = the angle of reflection. The incident sound ray, the reflected sound ray, and the normal to the reflecting surface at the point of incidence lie in one plane perpendicular to the reflecting surface. The sound that falls perpendicular to a reflecting surface is reflected on itself & therefore the ear doesn’t distinguish the two sounds.

Echo is the repetition of sound due to its reflection. When you clap your hand near a wall you can’t hear an echo. Th e reflected sound comes quickly from the wall that you can’t separate the sound from its reflection. Scientists found that humans can’t separate sounds if the time between them is 0.1 seconds. 36

m distance we must stand from reflecting surface in order to hear an echo. Calculating the minimu

The speed of sound in air is 340 m/s Distance travelled by sound in 0.1 s = 340 x 0.1 = 34 m (towards the reflecting surface then back to you) Distance between the reflecting surface & the reflecting surface = 34 Ăˇ 2 = 17 m

Echo is heard when : 1.

The reflecting surface is big such as walls, mountains or watery landscapes.

2.

The reflecting surface should be at least 17 meter far from the source of sound.

Using echo in technical & medical applications aď&#x192;&#x2DC;

Calculating the speed of sound in air

Steps:

1. Let a person stand with a stopwatch at a known distance (at least 300 m) from

another person who holds 2 lids. 2. Let the 2nd person bang the lids. 3. When the 1st person sees the other banging the lids he starts the stopwatch &

he stops it when he hears the sound. Record this time. The velocity of sound (v) =

2 x the distance in meters (d) Time in seconds (t)

A solved problem A girl produced a sound & heard its echo after 3 seconds . Calculate the distance between the shore and the cliff . The velocity of sound in air is 330 m/s. 330 = 2 d 3 d = (3 x 330 ) Ăˇ 2

= 495 m

37

b-

Concentration of Sound:

Sound reflected from a concave surface collect at a point known as the focus of the surface reinforcing the sound. Mosques & many conference halls have concaved ceilings to concentrate sound & make it clearer .

Gazelles & foxes have long concaved ears to concentrate sounds.

c-

Determination of sea depth and fish shoals:

The sonar device in the ship produces ultrasonic waves. A hydrophone receives the reflected sound waves from sea bed or fish shoals. The depth (d) = velocity of sound (v) x echo time (t) 2

( t ) is the time interval between transmitting and receiving the waves (echo time).

Detecting defects & flaws in metallic pipes & parts of factory machines to avoid disasters. d-

Ultrasonic waves are directed to the pipes & machines to be examined. The 38

variation in the intensity of reflected ultrasonic sounds detect cracks & welding defects.

e-

Medical diagnosis:

Ultrasonic waves are used in medical investigations and laboratory tests & in checking the state of an embryo, because diff erent parts of the body reflect ultrasonic waves in various intensities.

An ultrasound image of a fetus at 20 weeks

Bats transmit ultrasonic waves (50 - 100 kHz) and receive their reflected

waves .This helps them to findRead food &more: fly in the dark without hitting obstacles. Dolphins use a similar method to find its food in the sea.

Ultrasonics - body, used, water, type, form, energy, methods, air, parts, caus http://www.scienceclarified.com/Ti-Vi/Ultrasonics.html#ixzz1DOZxMbGS

Reducing noise: 1. Carpets absorb many sounds & prevent their reflection therefore th ey reduce

noise. 2. Factory machines are installed on rubber bases which absorb many sounds.

[1] â&#x20AC;&#x201C; Write the scientific term: 1. The repetition of the original sound due to its reflection. (----------------------) 39

2. The angle of incident equals the angle of reflection. (----------------------) 3. The incident sound ray, the reflected sound ray and the perpendicular line from the point of incidence on the reflecting surface, all lie on the same plane, Perpendicular to the reflecting surface.

(----------------------)

4. Collection of sound at a point due to its reflection on a concave surface.

(----------------------)

5. An instrument which is used to produce ultrasonic waves to check the presence of fish gathering [shoals]. (----------------------)

[2] Choose the correct answer: 1. -------------waves are used in medical examinations& identification of embryo's sex and his health condition. (Sonic – Infrasonic – Ultrasonic – Sonic& Ultrasonic)

3.Which of the following relationships is used to estimate the depth of sea bed? (d = t xv - V = t/2 x d - t = d/2 x v - d = t/2 x v )

[3] Give reasons: 40

1. The ears of fennec fox are big & concave. -----------------------------------------------------. 2. Dolphins don't hit any sea obstacles during swimming. -----------------------------------------------------.

[4] What happens when? The time separating the original sound produced& its echo was less than 0.1 sec. ----------------------------------------------------------------------------------------------------.

[5] Mention the importance of: 1. Sonar set: ------------------------------------------------------. 2. Hydrophone set: ----------------------------------------------------------------------------------------------------.

[6] What are the conditions required to hear an echo?

a.---------------------------------------. b.---------------------------------------.

41

[7] a. Complete the path of the ray: Source of sound

d= 600 m

a.Calculate the echo time: given that the speed of sound in air is 340 m/sec.

---------------------------------------------------[8] An ultrasonic wave is produced by a ship. The wave hit the sea bed & returned back after 0.1 sec. Calculate the depth of sea, given that the velocity of such wave in water is 1490 m/sec.

Solution

Lesson 3: The wave nature of light Analyzing white

light:

1. A glass triangular prism analyzes white light into many colors . 2. Each color has a certain frequency . When white l ight passes through the prism, 42

the colors deviate with different angles & analyze. 3. These colors known as the colors of spectrum are :

red, orange, yellow, green, blue, indigo and violet.

Physicist Max Planck proved that light waves consist of packets of energy called photons . The energy of the photons is directly proportional with (Îą) its frequency

The energy of photon = Planckâ&#x20AC;&#x2122;s constant x the frequency

Frequency Energy of photon A transparent medium

Examples air and pure water

Red light

Violet light

less

bigger

smaller

bigger

An opaque

medium Wood & metal

43

A

translucent

medium Flint glass

permits the light to

does not permit

permits part of the

pass through it.

light to pass

light to pass through it

through it.

and absorbs some light.

Light can pass through water to a certain depth. Therefore fish in the deep of River Nile aren’t seen since light doesn’t penetrate deeply.  Activity

1:

Aim : To prove that light travels (propagates) in straight lines

Tools: four cards – pieces of plasticine –

Steps:

a light pen – white A4 paper.

1. Make identical holes in the middle of three cards. 2. Fix the four cards using plasticine on the white paper plate, where the holes

lie on the same line. 3. Allow light of the light pen to pass towards the hole of card (a). 

Observation

A spot of light is formed on card (d). The light spot disappears if card (b) or ( c )is moved slightly to the left or right. 

Conclusion

Light travels through a transparent medium in the form of straight lines.  Activity 

2:

Aim: To identify light intensity (brightness) for a given surface .

Direct a torch towards the wall in a dark room. Change your distance from the

wall. 

Observation:

Light intensity is changed according to the distance between the source & wall. 44

ď&#x192;&#x2DC;

Conclusion

In position 2 ,the light incident on the unit area of the surface decreases.

Light intensity is the amount of light incident onto a unit area of a surface in one second. Light intensity decreases as the distance between the surface and the light source increases . The inverse square law of light states that light intensity of a surface is inversely proportional to the square of the distance between the surface and the source of light . The head lights of some cars are mercury lamps to give bright illumination that shows other cars in the fog. At night, this bright light impairs the vision of drivers of the cars coming in the opposite direction.

Q1. Choose the correct answer: 1.Light waves are ---------------Waves. a.Mechanical transverse.

c. electromagnetic transverse.

b.Electromagnetic longitudinal. d. mechanical longitudinal 2.The quantum of energy of green light is ----------- the 45

quantum of energy of yellow light. a.Greater than.

C. less than.

b.Equal to

d. no correct answer.

3.The human skin is considered a (an) ----------- medium. a.Transparent.

c. no correct answer.

b. Translucent.

d. opaque.

4.When the distance between the source of light and the surface of a wall decreases, the light intensity of the surface ---------. a.

decreases

b. is doubled

c. increases d. remains constant]

[2] Write the scientific term: 1. The main source of light energy on the earth surface. (--------------------) 2. A medium that doesn't allow light rays to penetrate through. (--------------------)

[3] Give reasons for: 46

1. The energy of red light photon is less than that of orange light photon. ---------------------------------------------------------------------------------------------------. 2. The inability to see the impurities present in black honey. -------------------------------------------------------------------------------------------------.

[4] What is meant by: 1.Visible light: ----------------------------------------------------------------------------------------------. 2.Light intensity: ----------------------------------------------------------------------------------------------.

[5] What happens when? 1. Incidence of white light ray on one face of a triangular prism. ------------------------------------------------------------------------------------------------.

47

2. The distance between the light source& a surface is doubled concerning the light intensity. -------------------------------------------------------------------------------------------------.

[6]

Write down the mathematical relation between:

1)-The photon frequency of a wave & its energy.

----------------------------------------------------.

[7] Cross out the unsuitable word, then write the scientific term: Yellow / Blue / White / Violet / Red.

----------------------------------------------------------------------------------------------------------------------------------------------------------------

48

Lesson 4:

Reflection & refraction of light st 1 reflection of light When light falls on a reflecting surface , light reflects . Reflection of light explains why we see inverted images of trees in pools of rain on the road. It also explains the formation of shadow of trees and buildings & other objects.

Types of reflection Regular reflection

49

Irregular reflection

Examples of the

a.

reflecting

b. Aluminum foil.

surface

c.

Definition

Plane mirror.

Stainless steel tray.

a.

A tree leaf.

b.

A piece of leather.

c.

A woolen jacket.

d. heStainless steel tray T incident light rays

The light rays

reflect uniformly in one

uniformly in different

direction.

directions.

The laws of light reflection  Activity

1:

Aim: To conclude the laws of light reflection

Tools: Plane mirror protractor. laser pen (warning: don’t look at the laser pen directly)

Steps

1.

Put the protractor in a vertical position perpendicular to a plane mirror placed on the surface of a table.

2. Direct the laser pen towards the plane mirror . The beam makes an angle of 30 ° with protractor. 3. Change the angle to 45° 4. Direct the beam perpendicular to the surface of the mirror .

Observation

Angle of incidence = angle of reflection

50

reflect non

Conclusion The laws of reflection of light are The angle of incidence = the angle of reflection . 2-The incident light ray, the reflected light ray and the normal at the point of incidence to the reflecting surface are in a plane perpendicular to the reflecting surface. The light ray perpendicular to the mirror is reflected on itself where the angle Of incidence = the angle of reflection = zero.

Technology uses light reflection: 1.

The periscope is used to see objects surrounding a

submarine or happening behind a wall or to monitor dangerous chemical reactions in a laboratory.

Mirror

2.

Optical fibers Medical endoscopes contain optical fibers are inserted in the

periscope

body to see internal organs. They use cameras to diagnose diseases & operate using lasers.

51

optical fibers

2

nd

Refraction of light

The path of a barrel on the asphalt is different from its path on sand because it moves with different velocity on each medium. Also light travels in different transparent media with different velocities.

Light refracts (change its path) when it passes from a transparent medium to another. The optical density of the medium is the ability of the transparent medium to refract light. 

Activity 2:

Aim: To conclude the laws of light refraction

Tools: Thick rectangular glass block – pencil–protractor - white paper sheet – ruler – laser pen .

Steps:

1. Draw the outline of the rectangular glass block on the paper sheet. 2. Direct a ray from the laser pen to the point of incidence (a) as in the figure.

Draw a straight line to represent the incident ray. 3. Draw the path of the emergent ray from the point (b) on the opposite side of

the rectangular prism. 4. Remove the rectangular prism .

52

5. Join (a) and (b) with a straight line to represent the refracted ray. 6. Draw at ( a ) and ( b ) dotted vertical lines , each represents the normal at the

point of incidence. ď&#x192;&#x2DC;

Observations

1. The angle between the incident ray and the normal at the point ( a ) = the angle of incidence.

2.The angle between the refracted ray and the normal at point (a) = the angle of refraction. 3.The angle between the emergent ray and the normal at the point ( b ) = the angle of emergence.

Conclusion Light refracts when it travels from a transparent medium to another transparent one of different optical density. The angle of incidence is the angle between the incident light ray and the normal at the point of incidence on the interface. The angle of refraction is the angle between the refracted light ray and the normal at the point of incidence on the interface. The angle of emergence is the angle between the emergent light ray and the normal at the point of emergence on the boundary surface.

Laws of light refraction

53

a. When a light ray travels from air to glass , the refracted ray moves towards the normal because the optical density of the 2nd medium (glass) is bigger than that of air (the 1st medium)

b. When a light ray travels from glass to air, it refracts away from the normal at the point of incidence. That’s because the optical density of the 1st medium (glass) is bigger than the optical density of the 2nd medium. c. When a light ray is perpendicular to the surface between

two transparent media, the light ray passes without changing its path (i.e. the light ray doesn’t refract). d. The ratio between the speed of light in air to that in another transparent

medium is the absolute refractive index of that medium (n) The refractive index (n)

=

Speed of light in air Speed of light in medium

The speed of light in air is bigger than its speed

through any transparent medium,

therefore the refractive index of any transparent medium is bigger than one.

A solved example Calculate the velocity of light in glass. The velocity of light in air equals 3x 10 8 m/s. The absolute refractive index of glass is 1.5 Speed of light (glass) = Speed of light (air) refractive index of glass

Speed of light (glass) = 3x 108 ÷ 1.5 = 2 x 108 m/s

 Activity

3: 54

Aim: To conclude the definition of the critical angle and total internal

reflection 

Tools:

Steps: Direct the flash light near the base of a trough filled with water at one

A trough of water. A flash light

of its sides. Change the angle of incidence. 

Observation

The light ray is refracted in the cases where the

angle of incidence is less than

48.6° The light ray is reflected back into water when the

angle of incidence is more

than 48.6°

Conclusion

a. When the light ray falls on the water surface with an angle larger than the

critical angle , light doesn’t pass through the boundary & is reflected . b. The critical angle is the angle of incidence above which the total internal

reflection occurs. c. Total internal reflection occurs when light travels from a high optical density

medium (water) to a lower density medium.

1. A pencil partially immersed in water appears as being broken due to refraction of light rays coming from 55

the immersed part in water.

1. Fish in a lake have an apparent position slightly abo ve its real position due to refraction of light rays away from the normal. The eye sees the

extensions of the refracted rays coming from the fish. 2. When you travel in the desert in very hot weather , you see a lake in the

distance which disappears as you get closer. This phenomenon is called mirage & is caused by light refraction. It happens because air near the hot ground is hotter than the air higher up. 3. The rays coming from a tree refract on traveling between layers of air of different temperature. Total internal reflection happens to the rays coming from the tree. This layer appears as a watery area and a virtual and inverted image of the tree is formed.

1 â&#x20AC;&#x201C; Write the scientific term: 56

1.The reflection in which the light rays recoil in many directions when they fall on a glistening surface. . (------------) 2. The ability of the medium to refract light rays. (----------) Changing the path of light when travels from a transparent medium to another of different optical density. (-------------) 4.The return [recoil] of a light ray when it is incident in a medium of larger optical density by an angle larger than the critical angle of this medium.

(---------------------)

[2]Complete the following: 1. Optical ----------- are used in the manufacture of medical ----------that are used to perform dangerous operations without surgery. 2.The angle of ------------is the angle between the refracted light ray & the -------------- at the point of incidence on the separating surface. 3. When you look at a coin in a glass of water, its ---------Position appears to be lower than -------------position.

[3] Give reasons for:

57

1. The light ray that is incident perpendicular on a glistening surface reflects on itself. ------------------------------------------------------. 2.The absolute refractive index for any transparent medium is always greater than one. ------------------------------------------------------. 3.Occurrence of mirage phenomenon in desert regions at noon. -----------------------------------------------------.

[4] What is meant by: 1. Absolute refractive index of water is 1.33 -----------------------------------------------------. 2. The critical angle of a transparent medium with respect to air equals 400. -----------------------------------------------------.

[5] Mention the function of: 1. Optical fibers. ----------------------------------------------------.

58

2.Periscope. ------------------------------------------------------------------------------------------------------------.

[6] calculate

the absolute refractive index of diamond given that

the speed of light through it is 1.25x 108 m/sec. Knowing that the velocity of light through air is 3x 108 m/sec.

Solution

[7] Complete

the path of the light rays, given that the angle of

incidence of light ray 2 equals the critical angle.

Glass

59

1 2 3 4 Water

Unit 3:

Reproduction continuity

& the of species

Lesson 1: Reproduction in plants

Lesson 2: 60

Reproduction in humans

Lesson 1: Reproduction in plants The flower is a short stem with modified leaves that form the genital (reproductive) organs .The seeds & fruits are formed inside the flower.

The structure of the bisexual

flower

• A flower arises from a flowering bud,

usually emerging from the axils of the leaf • •

known as bract .

The axis may carry a number of flowers known as the inflorescence. A flower has a thin neck that ends with a receptacle which carries the 4 whorls

of the flower: calyx, corolla, gynoecium & androecium Floral whorl

Calyx

Corolla

Androecium

Gynoecium

Leaves of the floral whorl Description

Sepals

Petals

Stamen

Carpels

Small green Leaves Surrounding the flower.

Colored,

Fine threads (filaments), each

A flask shaped ovary with a long hollow tube (style)

Scented leaves

ends with a sac

(anther).

that ends with an

opening (stigma) 61

Function

Protection of

a.Attracting

The anther has

a. Itâ&#x20AC;&#x2122;s the female

the internal

insects to

4 chambers that contain the

reproductive

parts of the flower specially

pollinate the flower. b.Protect

pollen grains.

the organs

organ. b.The ovary contains the ova.

of reproduction

before blooming

Comparison between unisexual & bisexual flowers P.O.C. Definition

Unisexual flowers a-

Contain the male reproductive organ

(androecium) only. b- Contain the female reproductive organ gynoecium only .

Bisexual flowers Contain male and female reproductive organs together. (hermaphrodite)

Examples

palms, maize and pumpkins

Tulip, petunia and wallflowers

Steps of reproduction - Pollination - Fertilization

62

- Pollination: When pollen grains mature , the anther splits up longitudinally, releasing pollen grains in the air.

Pollination is the transfer of pollen grains from anthers of a flower to the stigma.

Types of pollination: P.O.C. Method of pollination

Auto (self) pollination

Mixed pollination

pollen grains are transferred pollen grains are transferred from the anther to the

from the anther of a flower

stigma in the same plant

to the stigma of a different

plant

Examples

barley & maize

Sunflowers

Methods of cross pollination: The pollen grains are transferred from one flower to another by many ways:

Pollination by air: The anthers of some flowers hang out and their stigmas are feathery and sticky to catch pollen grains. These flowers are pollinated by air. They produce huge numbers of light dry pollen

grains where many are lost in the air.

Pollination by insects : Some flowers have colored, scented petals that 63

attract insects. Bees absorb the nectar in the flower.The pollen grains are sticky or have coarse surfaces to stick to the insect. Artificial pollination is done by the farmer who spreads palm tree pollen grains over the female flowers. In plants : Fertilization is the fusion of the male cell (pollen grain) with the (female cell) ovum.

Germination of pollen grains:  Activity

1:

Tools : Diluted sugar solution – glass slides and covers – water – microscope

Steps:

1. Put a drop of sugar solution onto a glass slide, then add pollen grains, and cover them with a plastic cover.

2. On another glass slide mix some pollen grains with water & put a plastic cover on the sample. 3. Put both slides in a dark warm place for half an hour. 4. Examine both slides using a microscope . 

Observation :

Steps of germination

Steps of germination

1. After pollination, pollens secrete a sugary solution. 2. The pollen grain forms a pollen tube containing two male nuclei and a tube nucleus. 3. The pollen tube extends through the style and reaches the ovum by the micropyle opening in the ovary. 4. One of the male nuclei fuses with the egg to form a 64

fertilized ovum which is

known as the zygote. 5. The zygote divides several times to form the embryo. 6. The embryo develops to become a seed & the ovary grows to become the fruit.

The number of seeds in th e

fruit differ according to the number of ova in the P.O.C.

the ovary contains one ovum

an ovary with many ova

a single seed

Many seeds

olives and peaches

beans and peas

No. of seeds in the fruit Examples

ovary .

Vegetative reproduction Sexual reproduction involves a male & female cell which join forming a zygote.

65

Plants also reproduce asexually where parts of a plant separate off & grow into a new plant.

In plants: asexual reproduction is known as vegetative reproduction. Vegetative reproduction may be. 1. By tubers: Some plants form swellings called tubers which store food. A tuber is a root like sweet potatoes or an underground stem like potatoes. A tuber of potato is cut into pieces so that each piece contains at least one bud (eye). Then the pieces are buried in the soil in the season of cultivation. From each bud a new plant emerges.

2.

By cutting:

One of the branches of the stem is cut into pieces, each cut containing 2 or more buds . These are planted before spring with some buds below the surface of the soil & some above the surface of the soil . Roots grow from the buds below the surface & leaves grow from the buds above the surface of the soil. • Examples are roses , grapes & sugar cane. • Cuts from leaves of some plants are used to produce new plants.

3. By grafting: •

A plant tissue (the

scion) such as a branch or a bud is attached to an already growing plant (the rootstock). A new plant

then grows from the scion.

Example : mango tree , orange tree , naring, apples and pears, peaches and apricots. Methods of reproduction by grafting: •

Attachment

Wedge 66

The scion is attached to the stock.

The scion in the form of a wedge (pencil shaped) is inserted into a cleft in the stock.

An example: mango trees

An example: large trees

Grafting of mango

Tissue culture Scientists use a small part of a plant to produce new plants. The plant tissue is placed in a culture medium containing nutrients and hormones The new plant grows on the medium.

An example : Tissue culture from potato.

67

[1] Write the scientific term: 1. Short stem where the leaves developed& modified into reproductive organs.

(-------------------)

2. The bisexual flowers.

(-------------------)

3. The cell resulting from the fusion of pollen grain and the ovum nuclei.

(----------------)

5. The reproduction of some plants by parts of the roots, stems or leaves.

(---------------------)

5. The flowers which contain both androecium & gynoecium. (---------------------) 6. A new method to produce large numbers of plants from a small part of it.

(--------------------)

[2] Put ( â&#x2C6;&#x161; ) or (x), then correct the wrong ones. 68

1. The wall of the ovary after pollination forms the coat of the fruit. ( ) 2. Reproduction by tuber happens in orange& bitter orange.(

)

[3] Give reasons: 1. The petals of corolla are colourful& scented. ---------------------------------------------------------------------------------------------------. 2. Palm flowers are unisexual. ---------------------------------------------------------------------------------------------------. 3.Auto pollination can't happen in sun flowers. ----------------------------------------------------------------------------------------------------. 4.Flowers pollinated by insects produce coarse pollen grains. -----------------------------------------------------

[4] Choose from column B& C, what's suitable for column A:

69

A

B

Floral whorl

C

Consists of

1.Calyx. 2.Corolla. 3.Androecium.

a.Stamens. b.Sepals. c.Carpel.

4. Gynoecium

d.Petals.

Function 1. 2. 3. of 4.

Male organ in flower. Female organ in flower. Protects the inner parts a flower. Attract insects to the

colored leaves.

[5] What happens? 1. When a pollen grain falls on the stigma of a flower. ----------------------------------------------------------------------------------------------------. 2. To the ovary after fertilization. ----------------------------------------------------------------------------------------------------. 3. To the zygote. ----------------------------------------------------------------------------------------------------.

[6] Cross the unsuitable word out, then write the scientific term: 1. Stigma / stamen / style/ ovary.

70

---------------------------------------------------. 2. Sepals / petals / tubers / carpels. ---------------------------------------------------. 3. Segments / pollination / tarqeed / insertion. ---------------------------------------------------.

Lesson 2: Reproduction in humans 1.

Like all higher animals , humans can only reproduce sexually. A sperm from a

man joins with an egg (ovum) in the woman to produce a new human individual . 2.

The offspring is different from the parents.

3.

The system responsible for reproduction in humans is called the genital system.

Male genital system is different in structure & function from female genital system.

Male genital system Structure: It consists of the testes, vas deferens, the urethra , the penis & the associated glands. Structure testes

Description

Function

Two elliptical glands

Produce :a. sperms (male reproductive cell)

Vas deferens

b. male hormones (testosterone) Sperms complete their growth & are

Looped tubes called epidedimis attached to each testicle

stored there . The sperms are released towards the urethra.

71

The

The seminal vesicle

associated

The prostate

glands

Cowper's gland

They secrete an alkaline fluid which is mixed with the sperms forming the seminal fluid.Their secretion neutralizes the acidity of urine & nourishes the sperms to keep them alive & help them flow easily.

The penis

Sponge like tissue .

Discharge of semen & urine.

The urethra travels through the penis.

Testosterone 1. Testator on is responsible for the signs of puberty which include appearance of moustache & beard, the change of voice & the growth of muscles & bones. 2. The testes are enclosed inside a sac is known as scrotum outside the body to keep the temperature of the organ two degrees below the internal temperature of the body. This is the temperature suitable for the growth and development of sperms. 3. If the testes where kept inside the body and didn't come out during the development of the embryo , the sperms would die .

The female genital system The human female genital system consists of two ovaries, fallopian tubes, the uterus and the vagina.

72

Structure Two Ovaries

Description

Function

Each gland has the size of a peeled almond

1. Each ovary produces one ovum every 28 days . 2. Secrete female hormones.

Each tube has a funnel shape

Two Fallopian tubes

& ends with finger like

They have muscular walls which contract then relax to push the ovum towards the uterus.

processes. Each tube joins the upper corner of the uterus

Pear shaped hollow organ found in the pelvic cavity.

The uterus

It has a muscular wall covered with a mucus membrane

The vagina

A muscular tube between the uterus & the external genital opening.

It expands during pregnancy so that the size of the uterus fits the growth of the embryo. The mucus membrane is rich in blood vessels. Which are attached to the placenta to nourish the embryo. It expands during labor to deliver the baby

Female hormones: 1- Estrogen is responsible for the secondary sexual characters in female . 2- Progesterone is needed for starting & maintaining pregnancy. 73

Signs of puberty in females: The growth of hair on some body parts , softness of voice, fat accumulates in the breasts & certain parts of the body, menstrual cycle every 28 days. Menstrual cycle occurs at teenage and stops at menopause

The ovum is the female reproductive cell It is a large static spherical cell (the size of a sesame seed) that stores nutrients. Ovulation is the production of ovum from the ovaries every 28 days.

The structure of the ovum Nucleus

It contains half the genetic material.

Cytoplasm

It stores nutrients

Cell

Coating the cell

membrane

The sperm is the male reproductive cell

The structure of the sperm Head

It contains half the genetic material.

74

Middle

It contains mitochondria that release energy needed to move the sperm.

part Tail

It helps the sperm to swim towards the ovum.

1.

The body of the living organism consists of cells.

2. 3.

The nucleus in the cell contains the genetic material called chromosomes. The chromosomes are responsible for the hereditary traits of the organism.

4.

The number of chromosomes for a certain species is constant. Humans have 46

chromosomes arranged in 23 pairs in all cells except reproductive cells which have half the number of chromosomes (23).

P.O.C.

Steps of fertilization Examples

No.Of chromosomes

Somatic cells

Reproductive cells

Muscle cells , skin cells

Ovums & sperms

Full number of

They contain half the

chromosomes

genetic material.

1.

The sperm secretes a material that dissolves the wall of the ovum penetrating it.

2.

The ovum encloses itself by a membrane to prevent the entry of other sperms.

75

3.

The nuclei of the sperm and ovum fuse together to form the fertilized ovum known as the

zygote that contains a nucleus with 23 pairs of chromosomes.

The placenta develops in the uterus , itâ&#x20AC;&#x2122;s a mass of blood vessels which connects the developing fetus to the uterus wall to allow nutrient uptake & gas exchange via motherâ&#x20AC;&#x2122;s blood vessels. It connects to the fetus via the umbilical cord.

Development of the embryo 1.

The zygote is propelled to the uterus where itâ&#x20AC;&#x2122;s implanted.

2.

The zygote divides several times to form a clump of cells.

3.

These cells grow and specialize into different types of tissues & systems.

4.

The development of the fetus (embryo) occurs in 9 month divided into 3 stages:

76

Duration The first stage

The first 6 weeks of

Development of embryo Formation of a head & eyes.

pregnancy The second stage

The third stage

7th week till 12th week of The face , genital organs & pregnancy

digits appear

13th week till it the 22nd

1. Development of bones &

of pregnancy.

circulatory system. 2. The embryo movements are

23rd week till delivery. The fourth stage

All body systems are completely developed through this stage.

The fetus could be delivered by the twenty eighth week because its respiratory system can breathe atmospheric air. When the embryo is completely developed , it inverts its position with the head towards 77 the cervices of the uterus.

Diseases of the genital system

puerperal sepsis disease Means of infection

Incubation period

Bacterial infection

of the female reproductive system after child birth.

1-4 days

Symptoms

Increase in body temperature, chilling, pallor, severe acute pains in the lower abdomen associated by secretions from the uterus with bad smell.

Prevention

Sterilizing surgical tools. Avoiding contact with patients. The mother should avoid exposure to cold air currents.

Incubation period is the period of time between catching an infection and appearance of symptoms on the patient. symptoms on the patient.

78

Syphilis disease Means of infection

Syphilis bacteria are transferred from an infected person by sexual contact. The bacteria can be transferred from the pregnant woman to her embryo.

Incubation period

2 to 3 weeks

Symptoms

- The formation of a painless hard ulcer on the genital organs. - Dark brass colored rash appears on the back and hands.

Complications

- Tumors in different parts of the body like of the liver, bones and parts of the genital system. - The brain may also be damaged and the patient eventually dies.

Healthy toilet seat cover A plastic medical cover in the form of an elliptical plastic frame - sold in pharmacies â&#x20AC;&#x201C; should be used in public toilets to avoid infection by some skin and genital diseases.

Q1. Write the scientific term:

79

1.An oval- shaped gland that produces male cells. (-------------------) 2.Two glands that produce the female cells in human females. (-------------------) 3.The period between the beginning of infection& the appearance of disease symptoms.

(-------------------)

[2] Choose the correct answer: 1. The right ovary in the female human produces a mature (ripe) ovum every -----------days. ( 24

-

28

-

34

-

56 )

2. Fertilization occurs when ------------ is formed. ( embryo

-

Zygote

- endometrium

- ovum)

3. An ulcer at the tip of the penis in male is due to -------infection. ( syphilis

- gonorrhea

- puerperal sepsis - germen measles)

[3] Complete the following: 1. The ------------ glands& ---------Glands are from glands associated with the male genital glands.

80

2. The ---------- hormone in male& the ---------- hormone in female are responsible for the appearance of secondary sex characters. 3. The sperm consists of -------------, middle part& --------.

[4] Mention the function of: 1. The middle part of the sperm. -------------------------------------------------------------------------------------------------------------. 2. The scrotal sac. -------------------------------------------------------------------------------------------------------------. 3. The uterus. ------------------------------------------------------------------------------------------------------------.

[5] Give reasons for: 1. Man can't reproduce asexually. ------------------------------------------------------------------------------------------------------------. 2. The male whose testicles are still present inside the abdominal cavity is infertile (sterile).

81

------------------------------------------------------------------------------------------------------------. 3. Fallopian tubes ligation is considered as one of the means of birth control. --------------------------------------------------------------------------------------------------. 4. The baby can be born in the 28th week of pregnancy. -------------------------------------------------------------------------------------------------------------. 5. A new labored mother should avoid air currents after delivery. --------------------------------------------------------------------------------------------------------------.

[6] Compare between : 1. The sperm and the ovum. (3 points only) ----------------------------------------------------------------------------------------------------------------------------------------------------------.

[7] Cross the unsuitable word out, then write the relation between the rest:

82

1. AIDS / Gonorrhea / Syphilis / Measles. ----------------------------------------------------.

2. Testes / Fallopian tube / vas deferens / Scrotum. ----------------------------------------------------.

83

SCIENCE G8 BOOKLET

SCIENCE G8 BOOKLET

SCIENCE G8 BOOKLET

SCIENCE G8 BOOKLET