5.9 is moderate earthquake; 6.0‐6.9 is a strong earthquake; 7.0‐7.9 is a major earthquake. If the magnitude on the Rich‐ Logarithm is used in Chemistry to find out pH value of a solu‐ ter scale is 8.0 or above, it is a great earthquake. It may on. pH is the measure of the acidi‐ cause severe damages to buildings and roads, serious casual‐ ty or alkalinity of a solu on. Solu‐ es occur. Earthquakes occur day and hour in different plac‐ on with pH lower than 7 is said to es. be acidic, while solu on with pH higher than 7 is said to be alkaline. Solu on with pH 7 is said to be neutral. The equa on to calculate the pH value is Chemistry
–log[ (H+)] (H+) is the concentra on of Hydrogen ions in a solu on. For example, a solu on has 0.001 M of Hydrogen ions. The pH value of the solu on will be –log (0.001)= 3. Solu on with pH 1,2 is a strong acid, such as Hydrochloric Acid ; while pH 5,6 is a weak acid, like Ethanoic Acid . Solu‐ on with pH 8,9 is a weak alkaline, for example ammonia ; while pH 13,14 is a strong alkaline, such as Sodium Hydrox‐ ide. Strong acid and base is compound that completely dis‐ sociate in water, while weak acid and base is compound that partly dissociates in water.
Physics
There was an earthquake happened on May 12, 2008, which is known as Sichuan earthquake or Wenchuan earthquake. Logarithm is used in Phys- The magnitude on the Richter Scale of this earthquake meas‐ ics to calculate the sound ured at 8.0, which means it caused a lot of casual es and intensity level. Sound Inten- destruc ons. sity level is used to describe sound level. The equation Astronomy to calculate the sound intensity level is
β = 10 log (I/I0) where I0 is the lowest sound intensity that can be heard by human. I0 is found to be 10-12 W/m2 by scientists. Sound intensity level is measured in decibels (dB).
In Astronomy, people use a scale called apparent magnitude For example, the sound intensity produced by a MP3 player is 10-4 W/m2. The sound intensity level will be 10 log (m) tomeasure brightness of a star seen by observers on the earth. It is measuredon a logarithmic scale. The dimmer the (10-4/10-12)= 80 dB. star, the larger is the magnitude. A bright star may have a If sound intensity level is lower than 10-12 W/m-2, people nega ve apparent magnitude. cannot hear thesound. If sound intensity level is higher than that value, there will be discordant sound. The apparent magnitude can be calculated by the formula Geography
m= C‐2.5 log b
Richter Scale in Geography is a logarithmic scale, which use where C is a constant and b is the brightness of a star. to quan fy the energy released during an earthquake. Rich‐ For example, the sun has an apparent magnitude ‐26.7, full ter Scale was developed by an American scien st called moon ‐12.6, Venus at it brightest ‐4.7. The faintest star ob‐ Charles Francis Richter in 1935. It is widely used in servable with the naked eye has an apparent magnitude 6. the world. The formula is Common logarithm is widely used in science. Logarithm is log E=1.5M+K also applicable in many different aspects. Can you find out where M is magnitude of an earthquake and K is a constant. other examples, such as applica on in engineering? When magnitude on the Richter Scale is less than 2.0, it is said to be a Microearthquake, most people cannot felt the earthquake and it is recordedby seismographs. When it is between 2.0 and 3.9, it is a minor earthquake, it rarely caus‐ es damage, but there may be shaking of indoor objects. If magnitude is 4.0‐4.9, it is said to be a light earthquake; 5.0‐
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