Electromagnetic Waves P1.6

Electromagnetic Waves P1.6

1. Electromagnetic spectrum

   • In order of decreasing wavelength & increasing frequency: Radio waves, Microwaves, Infrared, Visible light, Ultraviolet, X-ray, Gamma
   • V = f x λ used to calculate wave properties

2. Light, infrared, microwaves & radio waves

   • White light contains all visible colours of spectrum
   • Infra red used for carrying signals from remote handsets and optical fibres.
   • Microwaves used to carry satellite Tv programmes mobile phone calls
   • Radio waves for radio communication, mobile phones
   • Microwaves and radio waves can cause internal heating. infra red can cause skin burns

3. Communications

   • Radio waves of different frequencies are used for different purposes due to wavelength which affects: how far they can go, how much the spread, how much info they can carry
   • Microwaves used for TV signals
   • Research needed to evaluate whether mobile phones are safe to use
   • Optical fibres are thin fibres, used to transmit signals by light and infrared radiation

4. The expanding universe

   • Red shift of a distant galaxy is shift to longer wavelengths of light from it due to galaxy moving away from us
   • Faster a distant galaxy is moving away from us, the greater its red shift
   • All distant galaxies show red shift, further away it is the greater its red shift
   • Distant galaxies are all moving away from us because the universe is expanding

5. The Big Bang

   • Universe started with a big bang: massive explosion from a small initial point
   • Universe been expanding ever since big bang
   • Cosmic microwave background radiation CMBR is electromagnetic radiation created just after the big bang
   • CMBR can only be explained by the big bang theory