Electromagnetic Waves

• The electromagnetic spectrum (in order of decreasing wavelength and increasing frequency and energy) is made up of:

  • Radio Waves
  • Microwaves
  • Infrared Radiation
  • Visible Light (red to violet)
  • Ultraviolet Waves
  • X-rays and Gamma Rays
• The human eye can only detect visible light. The wavelenght of visible light ranges from just below 400nm to above 700nm.
• Electromagnetic waves transfer energy from a source to an absorber.
• Wave Speed = Frequency x Wavelength
• White light contains all the colours of the visible spectrum
• Infrared radiation is used for carrying signals from remote control handsets and inside optical fibres.
• Microwaves are used to carry satellite TV programmes and mobile phone calls. Radio waves are used for radio and TV broadcasting, radio communications and mobile phone calls.
• Mobile phone radiation is microwave radiation, and is also radio waves at near-microwave frequencies.
• Different types of elctromagnetic radiation are hazardous in different ways. Microwaves and radio waves can heat the internal parts of people's bodies. Infrared radiation cam cause skin burns.
• Radio waves of different frequencies are used for different purposes because the wavelength (and so the frequency) of waves affects:

  • How far they can travel
  • How much they spread
  • How much information they can carry
• Microwaves are used for satellite TV signals.
• Further research is needed to evaluate whether or not mobile phones are safe to use.
• Carrier waves are waves that are used to carry information. They do this by varying their amplitude.
• Optical fibres are very thin transparent fibres that are used to transmit communication signals by light and infrared radiation.
• Ultraviolet waves have a shorter wavelength than visible light and can harm the skin and the eyes.
• X-rays are used in hospitals to make X-ray images.
• Gamma rays are used to kill harmful bacteria in food, to sterilise surgical equipment, and to kill cancer cells.
• Ionising radiation makes uncharges atoms become charged.
• X-rays and gamma rays damage living tissue when they pass through it.
• X-rays are used in hospitals:

  • To make images of your inetrnal body parts
  • To destroy tumours at or near the body surface.
• X-rays are ionising radiation and so can damage living tissue when they pass through it.
• X-rays are absorbed more by bones and teeth than by soft tissues.