The electromagnetic waves

The electromagnetic waves

1. Electromagnetic spectrum

   • The electromagnetic spectrum(in order of decreasing wavelength, increasing frequency and energy)is: -radio waves -microwaves- infrared radiation -light -ultraviolet radiation -Gamma radiation and X-rays.
   • The wave speed equation is used to calculate the frequency or wavelength of electromagnetic waves

2. Light, infrared, microwaves and radio waves.

   • White light contains all the colours of the visible spectrum
     • Infrares radiation is used for carrying signals from remote handsets and inside optical fibres. We use microwaves to carry satellite TV programmes and mobile phone calls. Radio waves are used for radio and TV broadcasting, radio communications and mobile phone calls.
       • Different types of electromagnetic radiation are hazardous in different ways. Microwaves and radio waves can cause internal heating. Infrared radiation can cause skin burns

3. Communications

   • Radio waves of different frequencies are used for different purposes because the wavelength (and therefore frequency) of waves affects: -How fart they go -How much they spread -How much information they can carry
     • Microwaves are used for satellite TV signals
       • Need more info if mobile phones are safe to use
       • Optical fibres are very thin transparent fibres that are used to transmit signals by light and infrared radiation

4. The expanding universe

   • The red shift of a distant galaxy is the shift to longer wavelengths of the light from it because the galaxy is moving away from us
     • The faster a distant galaxy is moving away from us, the greater its red-shift is
   • All the distant galaxies show a red-shift. The further away a distant galaxy is from us, the greater its red shift is
   • The distant galaxies are all moving away from us because the universe is expanding