P2

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  • P2- radiation and life
    • The sun
      • UV radiation can cause skin cancer
        • UV appears just after the violet end of the visible light spectrum
      • Melanin (pigment in skin provides a little protection from UV)
      • Uv radiation is part of electromagnetic radiation
        • Spread out to form the electromagnetic spectrum
      • Need sunlight for vitamin D
        • Strengthens bones and muscles and boosts immune system
        • Darker skin makes it more difficult to absorb vitamin D
      • Reduces depression
    • Radiation models
      • All radiation has a source that emits it
        • It spreads out or radiates
        • Visible light causes a chemical changes at the back of the eye
      • Air is good at transmitting light
      • Objects would be invisible if it wasn't reflected off the object
      • Radiation from the sun includes infrared, visible light and UV
        • Some radiation is transmitted through the atmosphere
          • Most harmful UV radiation is absorbed by the atmosphere
            • Life depends on the ozone layer absorbing UV radiation
      • The atmosphere is a mixture of gases inc oxygen
        • Oxygen atoms form to make ozone O3
          • When UV is absorbed it can break ozone into oxygen
            • Reversible changes
        • Man made chemicals can form holes in the ozone layer that allows radiation through
    • Absorbing electromagnetic radiation
      • When materials absorb radiation they gain energy
        • Radiation can cause a varying electric current in metal wire
        • Radiation can cause heating
        • Radiation can cause chemical changes
        • Ionisation can damage living cells
      • Radiation arrives in pockets called photons
        • Sources emit radiation photon by photon
          • Absorbers gain the energy photon by photon
      • xrays, gamma rays and some UV are ionising
    • X-rays
      • Discovered in 1890s
      • Intensity  is the energy that arrives at a square meter of surface each second
        • Intensity is less the further away it is
      • Gamma is similar to x-rays but comes from radioactive materials
        • Both used to image internal organs
          • X-rays
            • Discovered in 1890s
            • Intensity  is the energy that arrives at a square meter of surface each second
              • Intensity is less the further away it is
            • Gamma is similar to x-rays but comes from radioactive materials
              • Both used to image internal organs
              • The radiation is more dangerous to quickly dividing cells (fetuses)
              • Reducing exposure to radiation
                • Time
                • Distance
                • Shielding
                • Sensitivity
        • The radiation is more dangerous to quickly dividing cells (fetuses)
        • Reducing exposure to radiation
          • Time
          • Distance
          • Shielding
          • Sensitivity
      • Heat
        • Microwave
          • Uses microwave radiation to transfer energy to absorbing materials
          • Water, fat and sugar are good absorbers
          • Microwave doors reflect the radiation to stop the microwave radiation cooking humans
        • Heating effect depends on intensity and duration/ time
        • Even things with temperatures below 0 degrees c emit infrared
      • Climate change
        • Climate- average weather in a region over many years
        • The Earth's average temperature is 15 degrees c
        • The earth's surface absorbs radiation from the sun, this warms theearth
        • The greenhouse effect
          • Greenhouse gases (carbon dioxide, methane and water vapor)
          • ]Absorb some infrared radiation which causes heating effect
        • The carbon cycle describes the stores of carbon and processes that move carbon
          • Co2 levels are rising
            • Human activities cause this
      • The future
        • Natural factors can also cause climate change
        • Scientists use computer models to predict what will happen with increasing CO2 levels
        • Climate changes causes:
          • Extreme weather
          • Rising sea levels
          • Drought and desertification
          • Health problems
        • Poor countries won't be able to deal with the effects of climate change
        • The gulf stream that keeps the UK at a mild temp may be slowing because of climate change
        • Technology can be used to reduce CO2 but will take a long time to develop and put into operation
      • Information
        • Mobile phones use microwaves
          • Radio waves of the highest frequency
          • Can travel long distances because they are only weakly absorbed by the atmosphere
            • Radio waves of the highest frequency
        • Can also be distributed using optical fibres (high purity glass- so less is absorbed)
        • Carrier wave+ information = signal
        • Digital signals only require two symbols, on and off
        • Continuous variation in waves is analogue
        • Microprocessor in phones decode information
          • Takes binary code and changes it to varying voltage which converts to noise
      • Digital signals
        • Can be processed by microprocessors
        • Can be stored in memories and take up little space
        • Can carry more information each second
        • Can be delivered without losing quality (no noise)
      • Health risks
        • Radiation leaving a mask is weak bythe time it reaches humans as it is spread out
        • Need to judge reliability of information given to us by studies
          • Look at how the sample participants are selected
          • Needs to be a large sample
          • Other factors

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