Science Benefits and risks Radiation that is not absorbed by the atmosphere reaches the Earth's surface and warms it, leading to the greenhouse effect. Some radiation, such as ultraviolet, exposes our skin to harmful rays and puts us at risk of developing skin cancer.
The atmosphere Some radiation of the electromagnetic spectrumelectromagnetic spectrum: The different types of electromagnetic radiation, arranged in order of frequency or wavelength. is absorbed by the atmosphere, but some is transmitted. Light, some infrared, some ultravioletultraviolet radiation: Electromagnetic radiation with a frequency between that of visible light and X-rays., and microwavesmicrowaves: Electromagnetic radiation with a frequency between that of visible light and radio waves., pass through the atmosphere and reaches the Earth’s surface. Gamma raysgamma radiation: High frequency electromagnetic radiation emitted during radioactive decay. Many centimetres of lead or metres of concrete are needed to absorb it., X-raysX-rays: High frequency electromagnetic radiation, used for medical imaging., most of the ultraviolet and some of the infraredinfrared radiation: Electromagnetic radiation emitted from a hot object. are absorbed by the atmosphere and do not reach the Earth’s surface.
Infrared Infrared from the Sun reaches the Earth’s surface and warms it
. The warm Earth emits some infrared radiation, and some of this is absorbed by gases in the atmosphere. This is called the greenhouse effect. If there were no greenhouse effect, the Earth would be too cold for life as we know it.
Photosynthesis Light from the Sun reaching the Earth’s surface provides the energy for plants to produce food by photosynthesisphotosynthesis: The chemical change that occurs in the leaves of green plants. It uses light energy to convert carbon dioxide and water into glucose. Oxygen is produced as a by-product of photosynthesis.. heating them. Photosynthesis replaces However, carbon dioxide in the atmosphere with ionising oxygen. This reverses the radiation process of respiration. s are more Microwaves likely to The atmosphere transmits damage microwaves, and these living can be used cells. to communicate with This is satellites. because photons Radiation and cell of damage ionising Any radiation absorbed by radiation living cells can damage them by deliver
Light from the sun reaching earth
much more information. DNA energy. stands for They can Deoxyribonucleic Acid. in easily kill the nucleus of a cell. cells, and can also cause cancer by damaging the DNADNA: Effects of microwaves The material inside the nucleus of cells, carrying genetic
Microwavesmicrowaves: Electromagnetic radiation with a frequency between that of visible light and radio waves. in the environment may be harmful, but there is no agreement on this. They are not ionising, and so cannot cause cancer in the way that ultravioletultraviolet radiation: Electromagnetic radiation with a frequency between that of visible light and X-rays., X-raysXrays: High frequency electromagnetic radiation, used for medical imaging. or gamma raysgamma radiation: High frequency electromagnetic radiation emitted during radioactive decay. Many centimetres of lead or metres of concrete are needed to absorb it. do. Microwave ovens work because the food contains water molecules which are made to vibrate by the microwaves. This means that food absorbs microwaves and gets hot. The microwaves cannot escape from the oven, because the metal case and the metal grid on the door reflect microwaves back into the oven. Some people microwaves is too think that Watch low to damage tissues by mobile You may wish to view phones, which heating, this BBC News item about campaigners winning a two-year battle to get a mobile phone mast moved away from a primary school. Watch
transmit and receive microwaves, may be a health risk. This is not accepted by everyone, as the intensity of the
and microwaves are not ionising.
Ultraviolet One health risk which is definitely present in our environment is ultraviolet, in sunlight. Not much of the ultraviolet reaching the Earth gets to us, because the ozone layer high up in the atmosphere absorbs most of it. In the summer, it is wise to use sun-screens and clothing to absorb ultraviolet, and prevent it reaching the sensitive cells of the skin.
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However, this will take a few years. It is important to be able to assess the size of risk in any activity. No activity is completely safe.
The consequence of too much ultraviolet – skin cancer – often does not appear until much later in life, so it doesn't seem a real risk to young people. It is difficult to assess how much ultraviolet you are receiving when you are sunbathing. If you feel hot, that is because of the infrared, not the ultraviolet. Weather forecasts now inform you of the intensity of ultraviolet radiation. See for example BBC weather. Benefits For most risky activities, there are benefits as well as risks:
sunbathing produces a sun tan, which many people find more attractive some ultraviolet is good for you, as it produces vitamin D in the skin Now try a Test Bite - foundation. Read on if you are taking the higher paper.
Making a judgement - higher only To make a judgement about a possible bad outcome you need to consider two factors:
What is the chance of the outcome happening? What is the consequence of that outcome? The precautionary principle The ‘precautionary principle’ tells you to avoid any activity if serious harm could arise.
Parents may insist that their children are not allowed out on the beach at all in the summer months. The real risk may be very different from the perceived risk ie the risk that you think is there.
You can’t see ultraviolet, and the word ‘radiation’ sounds frightening to many people. This makes the risk seem worse than something you can see, and which is more familiar. Some parents may assume that summers are no different from when they were young, so there is no danger to their children. Other parents may be very alarmed by stories of increases in skin cancer, and not let their children out in sunny weather at all. This is the precautionary principle. The ALARA principle The ALARA principle is to make any risk As Low As Reasonably Achievable. This usually applies to an organisation which is responsible for its employees.
a company employing lifeguards on the beach may insist that they wear lycra sun-suits and sun-screen cream to absorb ultraviolet when they are on duty the company may also arrange that lifeguards take turns at covering the hottest part of the day, when the intensity of ultraviolet is greatest Now try a Test Bite - higher. Back to Revision Bit