Benefits and risks

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phicysics (Radiation and life) Mind Map on Benefits and risks, created by jakeogilvie on 08/05/2013.
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Mind Map by jakeogilvie, updated more than 1 year ago
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Created by jakeogilvie over 11 years ago
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Benefits and risks
  1. The atmosphere
    1. Some radiation of the electromagnetic spectrum is absorbed by the atmosphere, but some is transmitted.
      1. Light, some infrared, some ultraviolet, and microwaves, pass through the atmosphere and reaches the Earth’s surface. Gamma rays, X-rays, most of the ultraviolet and some of the infrared are absorbed by the atmosphere and do not reach the Earth’s surface.
        1. Infrared
          1. 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 was no greenhouse effect, the Earth would be too cold for life as we know it.
          2. Photosynthesis
            1. Light from the Sun reaching the Earth’s surface provides the energy for plants to produce food by photosynthesis. Photosynthesis replaces carbon dioxide in the atmosphere with oxygen. This reverses the process of respiration.
            2. Microwaves
              1. The atmosphere transmits microwaves, and these can be used to communicate with satellites.
            3. Radiation and cell damage
              1. Any radiation absorbed by living cells can damage them by heating them. However, ionising radiations are more likely to damage living cells. This is because photons of ionising radiation deliver much more energy. They can easily kill cells, and can also cause cancer by damaging the DNA in the nucleus of a cell.
                1. Effects of microwaves
                  1. Microwaves 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 ultraviolet, X-rays or gamma rays do.
                    1. 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.
                      1. Some people think that mobile phones, which transmit and receive microwaves, may be a health risk. This is not accepted by everyone, as the intensity of the microwaves is too low to damage tissues by heating, and microwaves are not ionising.
                      2. Ultraviolet
                        1. 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 sunscreens and clothing to absorb ultraviolet, and prevent it reaching the sensitive cells of the skin.
                        2. The ozone layer - Higher tier
                          1. The ozone layer absorbs ultraviolet because ultraviolet ionises the ozone, which then changes to oxygen. This chemical change is reversible, and the oxygen changes back to ozone.
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