P2 - Radiation & Life

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  • P2 - Radiation & Life
    • Electromagnetic Radiation
      • Radiation = transfer of energy
        • Energy is delivered as photons
          • Photon = tiny 'packet' of energy
            • Amount of energy carried by photon depends on frequency of the radiation
              • Total energy = no. photons x energy per photon
              • Intensity = how much energy hits each square metre of surface per second (W/m2)
            • If light is absorbed the energy is passed on to the object
          • Amount of energy carried by photon depends on frequency of the radiation
            • Total energy = no. photons x energy per photon
            • Intensity = how much energy hits each square metre of surface per second (W/m2)
      • EM Spectrum
        • Radio waves, microwaves, infra red, visible light, ultra violet, x-rays, gamma rays
        • All travels at the same speed
      • An object that emits radiation is called a source
      • Transmitted = passes through things (eg. glass)
      • Reflected = bounces back (eg. mirror)
      • Absorbed = light taken in (eg. sunbather) - detector
    • Ionisation
      • Photons sometimes have enough energy to remove an electron from an atom
      • Can only be done by radiation with high energy
      • Can cause DNA to mutate when the cells divide over & over again - this is cancer
      • Protection
        • UV - clothes, suncream
        • X-rays - lead shields, lead aprons, concrete
      • Can kill cells
    • Uses of EM radiation
      • Cooking food
        • Infra red - toasters, grills
        • Microwaves - microwaves
          • Make particles vibrate, making them heat up
            • Strongly absorbed by water molecules
          • Strongly absorbed by water molecules
          • High power = high intensity so less cooking time
    • EM waves & communication
      • Radio waves & microwaves used
        • Not absorbed by earth's atmosphere much
          • Satellites for TV & phones
    • Global warming
      • Rise of carbon dioxide causing global warming by increasing greenhouse effect
      • Rise in sea level due to melting ice
      • Extra heatin atmosphere causes strong winds
      • Drought & floods
    • EM radiation & the atmosphere
      • Energy from sun is absorbed by earth
        • Earth radiates some of this hear
          • Energy is absorbed by greenhouse gases
            • Energy is re-radiated in all directions
      • Part of the atmosphere is called ozone = absorbs UV
        • UV splits a normal O2 molecule and adds the single O to another O2 molecule
          • This creates O3 which is ozone
        • Loss of ozone makes holes in the ozone layer
          • More UV gets to us
    • Analogue & Digital Sounds
      • All info is converted into electrical signals before it's transmitted
      • Both signals weaken as they travel so have to be amplified
        • Pick up noise/ interference en route
      • Digital = either on or off
        • Much higher quality
      • Analogue = take any value in a particular range

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