P2

P2

1. EM radiation

   • Radiation travels in photons
     • They travel in waves
     • An object emits the radiation
       • Travels outwards from an object and it can be reflected, transmitted or absorbed
     • Radiation can affect another object (detector) from a large distance when it is absorbed
     • The higher the frequency of the radiation the more energy is being transferred
     • Radiation travels at 300 000 km/s
     • You can measure the intensity by seeing to measure the energy that arrives at every square meter
     • The intensity of a beam decreases with the distance that it travels
       • UV, X-Rays and Gamma Rays have enough energy to change atoms or molecules
         • They can ionise cells in the body which can lead to cancer
         • They have enough energy to remove an electron from an atom, so they can cause ionisation
         • X-Rays can be absorbed by dense materials, such as bones and metals
   • How can radiation affect the body?
     • Heat from radiation can cause damage to living cells
       • The higher the intensity and duration the body is exposed to the more damage caused in the body
         • This can lead to death or cancer
     • Some people are concerned with low radiation microwaves and phones because they emit radiation
       • There is scientific evidence that they are not harmful
     • Microwaves are strongly absorbed by things containing water, when absorbed it heats up the object
       • Microwaves have a metal screen protecting the door to absorb the radiation and not let it get outside of the microwave
   • The ozone layer protects Earth from UV radations
     • Sunscreens and some clothing can be used to absorb UV radiation and protect us
   • Everything emits radiation

2. Global Warming

   • Earth is surrounded by an atmosphere that allow some EM radiaion to get through it
     • This radiation warms up Earth's surface
     • Some of that radiation is reflect back to the sun
     • The main greenhouse gas in Earth's atmosphere is CO2
   • Human activities are causing global warming
   • Climate change makes it impossible to grow crops in certain regions
   • More extreme weather events are likely to happen
   • Rising sea levels = more flooding

3. EM radiation and Communication

   • Some radio waves are not strongly absorbed by the atmosphere, so they are used to carry signals
   • Analogue signal= signal that can vary continuously
     • Analogue signals pick up interference or noise from electrical disturbances
   • Digital signal = a signal that can only take a discrete number of values (2)
     • The signal is carried out by the electromagnetic carrier switching on and off
       • Made up of 2 signals, '1' and '0'
       • 0 = no pulse
       • 1=pulse
     • Information can be stored and processed by computers
   • Information is stored in Bytes
     • The higher the amount of the information stored, the higher the quality of the image or the sound

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