SP5

• Electro-magnetic spectrum


  frequency range of electro-magnetic waves
• Opaque objects


  -Do NOT transmit light
• Converging lenses


  Bulges outwards in the middle

  -Causes rays to be brough together
• Diverging (concave) lenses


  Cave inwards

  -Causes rays to diverge
• Primary colours


  Red

  Blue

  Green
• Translucent and transparent


  Transmit light
• Colour filters


  Let through particular wavelengths
• The principle focus of a diverging lens


  Point where rays hitting the lens parallel to the acid appear to all come from
• The principle of a converging lens


  Where the rays hitting the lens parallel to the axis meet
• Focal length


  The distance from the centre of the lens to the principal focus
• How are images formed?


  When light easy from a certain point on an object appear to come together
• 2 types of images formed by lenses

  1. Real image
  2. Virtual image
• EM waves

  1. Radio waves
  2. Microwaves
  3. Infra red
  4. Visible light
  5. Ultra violet
  6. X-rays
  7. Gamma rays
• Key fact about EM waves

  The increase in frequency means the decrease in wavelength
• Uses of EM waves

  Radio waves

  Used for communication and broadcasting

  eg Bluetooth
• Uses of EM waves

  1. Infra red- monitor temperature
  2. Visible light- photography
  3. Ultra-violet- used in fluorescent lamps
  4. X-rays- let us see things inside
  5. Gamma rays- used to sterilise things
• Dangers of EM waves


  The higher the frequency, the more energy it transfers so the more potentially dangerous it is for humans
• Effects of EM waves on the body pt1

  1. Radio waves- are not absorbed
  2. Microwaves- can be absorbed and cause heating of cells
  3. Infrared/ visible light- mostly reflected or absorbed by skin. IR can burn skin
• Effects of EM waves on the body pt2

  1. UV- absorbed by skin. Can lead to skin cancer and damage your eyes
  2. X-rays/ gamma rays- ionising like UV can cause mutations and are absorbed by the skin
• EM waves


  Are transverse waves