P1.2 The EM Spectrum

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  • Created by: SanaaM
  • Created on: 25-02-16 20:36
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  • P1.2 The EM Spectrum
    • 1.Infrared and Ultraviolet
      • IR Radiation was discovered by Herschel - he found temperatures increased beyond the red end
        • Wavelength of IR  is longer than visible light
        • The frequency of IR is lower than visible light
      • UV Radiation was discovered by Ritter - Rate of reaction of silver chloride increased most beyond violet.
        • The wavelength of UV is shorter than visible light
        • The frequency of UV is is higher than visible light
    • 2. EM Waves
      • Properties of EM Waves = all transverse, can travel through medium, travel at same speed as light
        • Can transfer energy NOT matter
        • Can be reflected, refracted or diffracted
      • EM Spectrum Mnemonic - Radioactive Mice Invade Venus Using X-Ray Guns
    • 3. Uses of EM Waves
      • Visible Light - photography, vision, illumination
      • UV - Security (as absorbs UV and remits Visible Light, kill bacteria, used to disinfect sewage/water
      • X-Rays - Security (scanners used in airports, detect broken bones
      • Radio Waves- detected by aerials,TV and radio broadcasts, communicatin
      • IR - object give out IR (even us) Rescue service use it to find survivors under rubble , cook food (toasters)
      • Microwaves- cook for, communication with mobile phones.
      • Gamma Rays - Sterilizer food(kill of bacteria), removes germs from medical instruments, detects and treats cancer
    • 5. Ionising Radiation
      • Alpha Particles
      • Beta Particles
      • Gamma rays
    • 4. Dangers of EM Waves
      • Microwaves- cause internal heating of body cells (water)
      • IR - absorbed by skin(feel heat), too muchcan damage cells/burn skin
      • X-Rays - carry a lot of energy, excess exposure can cause genetic mutation  cancer)
      • UV - damage DNA, exposure to sun=skin cancer, damage eyes (cataracts)


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