P1.6

P1.6

1. the electromagnetic spectrum

   • radio waves, microwaves, infrared, light, ultraviolet, gamma and x rays
     • in order of decreasing wavelength increasing frequency
   • to remember: red monkeys in venus usually x-ray giraffes

2. light, infrared, microwaves and radiowaves

   • white light contains all the colours of the visable specturm
     • red, orange, yellow, green, blue, indigo, violet
       • Richard Of York Gave Battle In Vain
   • infrared carries signals, for example remote controls
   • microwaves carry information for example satellite
   • radio waves are used for communications for example radio
   • micro and radio waves can cause internal heating
   • infrared can cause skin burns

3. communications

   • radio waves for different frequencies are used for different things
     • different wavelengths affect:
       • how far they go
       • how much they can spread
       • how much information they can carry
   • microwaves are used for satellite TV signals
   • optical fibres can transmit signals by light and infrared

4. the expanding universe

   • red-shift is the increase of wavelenth of waves emitted by a star or galaxy as it is moving away from us
   • a galaxy that is moving away from us faster has a higher red-shift
   • all distant galaxies show red-shift, if it is further away it has higher red-shift
   • all galaxies are moving away from us as the universe is expanding

5. the big bang

   • the universe started with the Big Bang, a massive explosion from a small point
   • the universe has been expanding since the big bang
   • cosmic microwave background radiation (CMBR) is electromagnetic radiation created just after the Big Bang
   • CMBR can only be explained using the BB theory