chapter 13

• electromagnetic wave spectrum


  from radio waves with longer wavelength and lower frequency, to gamma rays with shorter wavelength and higher frequency

  radio waves, microwaves, infrared, visible light, ultraviolet, xrays, gamma rays
• properties of electromagnetic waves

  • has transverse wave, direction of vibration is perpendicular to direction of wave travel
  • made up of oscillating electric and magnetic fields, do not carry electric charge
  • can travel without a medium, same speed of 3x10^8 in a vacuum
  • wave speed equation, v=f(wavelength)
  • when an electromagnetic wave travels from a vacuum to another medium, wavelength and wave speed decreases but frequency stays the same at the source
  • undergo reflections and refractions
  • transfer energy
  • high temperature bodies emit more and higher frequency electromagnetic waves
• ionising waves


  those with higher frequencies and hence higher energies

  can eject electrons from atoms and molecules to create ions

  ions can cause harm by disrupting cell functions and even killing them
• uses of radio waves

  radio and satellite communication

  tv broadcast

  radio frequency identification tag
• uses of microwave


  microwave oven

  wifi signals

  radar
• uses of infrared


  heating

  short range data transfer
• uses of visible light

  artificial light for plants

  data transfer in optical fibres
• uses of ultraviolet


  sterilisation

  killing bacteria and viruses
• ultraviolet


  suitable dose of uv light enables our body to produce vitamin d that is good for our bones, muscles and immune system

  in regions with less sunlight, people use sun tanning beds to get a ore tanned skin tone but they have to exercise caution as overexposure can have harmful effects, including skin cancer and premature aging
• uses of x ray


  medical imaging

  find defects in manufactured parts

  energetic xrays can also be used to kill cancer cells
• uses of gamma rays

  most energy waves in the electromagnetic waves spectrum

  killing germs in food

  sterilising medical equipment

  radiotherapy

  detect defects in manufacturing

  treat cancer
• harmful effects of electromagnetic waves

  ionising radiation

  • high frequency electromagnetic waves or high energy particles
  • high frequency electromagnetic waves can penetrate our body more easily than high energy particles
  • high frequency electromagnetic is more harmful than high energy particles
• heating


  exposure to strong ionising electromagnetic waves such as uv light causes heating effects

  heating effects like skin cancer and premature aging
• ionising electromagnetic waves


  ultraviolet

  x ray

  gamma rays
• non ionising electromagnetic waves

  radio waves

  microwaves

  infrared

  visible light