P2 - Radiation and Life

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  • P2 - Radiation and Life
    • The Electromagnetic Spectrum
      • Seven radiations
        • 1) Radiowaves
          • e.g. Radios
        • 2) Microwaves
          • e.g. Telephone Masts
        • 3) Infrared
          • e.g. Remote Controls
        • 4) Visible Light
          • e.g. The Sun
        • 5) Ultraviolet
          • e.g. Sun Beds
        • 6) X-Rays
          • e.g. X-Ray Machines
        • 7) Gamma Rays
          • e.g. Some Stars
      • Contains 'packets' of energy called Photons
        • Different radiations = different amounts of energy
      • Intensity of beam
        • Number of photons every second
        • Amount of energy carried by each photon
        • Higher the freq = more energy
    • Intensity and Heat
      • Energy arriving at a square metre of surface per second
      • Depends on number of photons delivered per sec. And amount of energy each contains.
      • Further you atre from the source, the lower the intensity.
        • Photons spread as they travel - energy more spread.
        • Some photons absorbed by substances they pass through
        • Some photons are reflected and scattered
      • When materials absorb radiation, they heat up
        • Temp. increase depends on intensity.
        • Depends on duration of exposure
    • Ionising Radiation
      • Some radioactive materials emit ionising gamma radiation.
        • It has photons with enough energy to remove an electron from an atom or molecule to from ions.
          • Ions are very reactive - may take part in other chemical changes
            • Ionising Radiation
              • Some radioactive materials emit ionising gamma radiation.
                • It has photons with enough energy to remove an electron from an atom or molecule to from ions.
                  • Ions are very reactive - may take part in other chemical changes
                • Ultraviolet
                • X-Rays
                • Gamma
                • Cell Damage
                  • Heating effect can cause damage
                  • Ionising radiation damage skin cells
                  • Ionising radiation can cause mutations in nucleus of cell - may cause cancer
                  • Different amounts of exposure = different effects
                • Radiation Protection
                  • Microwave Ovens
                    • Used to heat objects containing water
                    • Metal case to reflect microwaves - prevents radiation from escaping
                  • Mobile Phones
                    • Low-intensity microwaves
                    • May be a correlation between usage and health problems
                  • Sunscreen - absorbs UV from sun, prevents skin cancer.
                • Using Absorption
                  • X-Rays
                    • Absorbed by dense materials - show shadow pics of bones.
                  • Protected by lead and concrete
                  • Radiation from sun warms earth when absorbed
        • Ultraviolet
        • X-Rays
        • Gamma
        • Cell Damage
          • Heating effect can cause damage
          • Ionising radiation damage skin cells
          • Ionising radiation can cause mutations in nucleus of cell - may cause cancer
          • Different amounts of exposure = different effects
        • Radiation Protection
          • Microwave Ovens
            • Used to heat objects containing water
            • Metal case to reflect microwaves - prevents radiation from escaping
          • Mobile Phones
            • Low-intensity microwaves
            • May be a correlation between usage and health problems
          • Sunscreen - absorbs UV from sun, prevents skin cancer.
        • Using Absorption
          • X-Rays
            • Absorbed by dense materials - show shadow pics of bones.
          • Protected by lead and concrete
          • Radiation from sun warms earth when absorbed
      • The Ozone Layer and Global Warming
        • Ozone layer absorbs some UV from sun.
        • Energy from UV causes chemical changes in the upper atomsphere.
        • The Earth emits EM radiation into space
          • Some gases in atmosphere absorb or reflect some of this radiation
            • Keeps Earth warm - Greenhouse Effect
        • Increased GHG in atmos. means amount of absorbed radiation from sun increases.
          • Increases temp. of Earth - Global Warming.
            • Climate change
            • Extreme weather conditions.
            • Rising sea levels
      • Signals and Transimtting Information
        • To create signal, info. put onto electromagnetic carrier waves.
        • Wave must be moldulated to carry a signal.
          • Changing carrier wave to create variation that matches the info. being transmitted.
            • Pattern on variation decoded by reciever
              • Original info
        • Analogue Signals
          • Varies continously
          • Amplitude /frequency takes any value.
            • Hard to distinguish between noise and original signal.
              • Noise cannot be completely removed.
          • e.g. Sound Wave
          • Noise = hissing sound
        • Digital Signals
          • Sound and images
          • Not continously varying
          • Digital signals made up of two symbols - 1 (on) and 0 (off)
          • On and Off - short bursts of waves.
          • Benefits
            • Transmitted signals have to be amplified at intervals to make them stronger
              • Pick up noise - reduces quality of signal
            • Easier to remove noise and recover original signal
            • Travel long distances and recieved at higher quality than analogue.
            • Info can be stored

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