Physics-Electromagnetic waves

The electromagnetic spectrum

• The electromagnetic spectrum (in order of increasing wavelength is: gamma rays, X-rays, ultraviolet, visible, infrared microwaves, radiowaves
• v=f x (upside down y) can be used to calculate the frequency or wavelengthof electromagnetic waves

Light, infrared, microwaves and radio waves

• White light contains all the coloura of the spectrum
• Visible light, infrared radiation, microwaves and radio waves are all used for communucation

Communications

• Radio waves of different frequencies are used for different purposes
• Microwaves are used for satellite TV signals
• Research is needed to evaluate whethere or not mobile phones are safe to use
• Optical fibres are very thin fibres that are used to transmit signals by light and infrared radiation

The expanding universe

• Light from distant galaxies is red-shift
• Red-shift provide evidence that the universe is expanding

The Big Bang

• The universe started with the Big Bang; a massive explosion from a very small initail point
• The universe has been expanding ever since the Big Bang
• Cosmic microwave background radiation (CMBR) is electromagnetic radiation created just after the Big Bang
• At present CMBR can only be explained by the Big Bang theory