Physics

Physics

1. P.2 Radiation and life

   • Electromagnetic radiation
     • There are 7 different types of radiation
       • Radio waves
       • Microwaves
       • Infra red
       • Visible light
       • Ultra light
       • x-ray
       • Gamma rays
     • Transfer of energy
       • This energy is delivered as photons
       • Photons are like pockets of energy
         • Not all photons carry the same amount of energy
   • EM Radiation and Energy
     • Transmitted
       • Just keep going, like light passes through glass
     • Reflected
       • Bounce back, like light reflected on a mirror
     • Absorbed
       • Like a sunbather absorbing UV rays through the sun
     • Intensity
       • Decreases with distance from the source because
         • The beam spreads out
         • The beam gets partially absorbed as it travels
       • Total energy = number photos x energy of each photo
   • Ionisation
     • All substances are made atoms and molecules
       • A photon hits an atom
         • Sometimes it has enough energy to remove an electron
           • This changes the atom or molecule
     • The dangers
       • Can damage the DNA molecules causeing mutation
         • Cancer
       • UV radiation can lead to sun burn and can damage living cells in the skin
         • Cancer
     • Protection
       • UV
         • Physical barriers
           • Clothes
           • Sun cream
       • X-Rays
         • Lead
           • Aprons
           • Shields
           • Lead absorbs X-Rays
   • Uses of EM Radiation
     • Heating
       • Microwaves
         • Cause particles to vibrate, heating them up
         • Metal cases and screens over their glass doors which reflect and absorb
     • Risks
       • When you make a phone call the same microwaves used to heat up food are produced
         • This when put to your head can cause cells to be damaged or die
           • Cancer
         • We use phones everyday so we are exposed everyday to radiation
   • EM radiation and the Atmosphere
     • The atmosphere keeps us warm by trapping heat
     • Green house effect
       • The Earth absorbed EM radiation from the sun.
         • The Earth then emits some EM radiation back into space
           • These are absorbed by green house gases
             • Carbon dioxide
             • Methane
             • Water vapour
             • These gases then re-radiate heat in all directions, including back towards the Earth
     • The ozone layer
       • UV radiaiton splits an ordinary oxygen molecule
         • into two oxygen atoms.
           • One of these oxygen atoms combines with another O2 molecule
             • to form an ozone molecule O3
       • Protects us from UV radiation
   • The Carbon Cycle
     • Respiration returns CO2 to the atmosphere as part of the carbon cycle
       • Photosynthesis in green plants and other organisms removed carbon dioxide from the atmosphere
         • Carbon dioxide is removed from the air and added to the air in approximately equal quanities
     • Human effects
       • Lifestyles
         • We use more electrical gadgets, and travel by planes and cars
       • Population is increasing so is the C02 levels
   • Global warming and climate change
     • Green house effect
       • This has been effected which cause global warming
         • As co2 levels are rising the earth is starting too warm up too much
           • Global warming
     • Consequences
       • Due to the temperature rising ice caps melt causing the sea levels
         • Causing the flooding of low lying places
           • E.g Maldives and the Netherlands
       • Change in weather patterns causing more extreme wether
         • e.g Hurricanes and extrem heat
         • Change in weather can also cause the for production to be affected
   • EM waves and Communication