P2- radiation and life

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  • P2- radiation and life
    • radiation is just the transfer of energy
      • visible light is the radiation our eyes can see: ROYGBIV
      • EM radiation is emitted from a source and can go through a vacuum, so will travel until it hits matter
    • EM spectrum (starting with lowest energy and frequency)
      • radio waves, micro waves, infra red, visible light, ultra violet, x-rays and gamma
    • energy is delivered as photons by all radiation
      • higher frequency means more energy in photons
      • frequency of thermal radiation increases with temperature
    • what happens when radiation reaches something
      • transmission (light through glass)
      • reflection (light on a mirror)
      • absorption (uv on a sunbather)
        • when radiation is absorbed photons transfer their energy
    • ionising radiation eg gamma- photons collide with atoms, and an electron is pushed out
      • if happens in  nucleus can  as random DNA changes and mutation, CANCER causing
    • protection from radiation- UV: clothes or sunblock, X-rays: lead shields or concrete blocks
    • uses of EM radiation
      • microwaves- vibrate water particles heating it
        • health risks- some absorbed by body, heat particles ad damage them
      • normal ovens- infra red to heat food
    • atmosphere- absorbs some radiation (keeps planet warm) some pass through eg visible light
    • ozone- O^3, formed when uv radiation splits an O^2 molecule and an O atom joins with an O^2 molecule forming ozone
    • carbon cycle
      • into atmosphere- respiration, combustion, bacteria and fungi breaking down matter
        • human activity is unbalancing carbon cycle
          • global warming- sea levels up, lan loss, extreme weather, food production change
      • out of atmosphere- photosynthesi-s
    • EM communication: infra red- tv remote, radio waves- radio, micro wave- mobiles
      • radio and micro- good long distance, no interference
        • low frequency
      • infra red and light are used in fibres, reflect of a wires plastic tube
    • info can be changed to an electrical signal, then sent long distance or superimposed onto a EM carrier wave
      • analogue- wave, every value between two points, so when amplified the interference means original signal can be hard to determine
      • digital- only transmits two values, so when amplified the original signal can be seen- better quality


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