Movement from the rest position.

• Wavelength: Measured in metres. The distance a wave travels before it repeats itself.
• Frequency: Measured in Hertz (Hz). The number of waves per second.
• Amplitude: Measured in metres. The maximum displacement.

Longitudinal: The displacement is in the same direction as energy transfer.

Transverse: The displacement is across the direction of energy transfer.

Wave speed = (1/Frequency) x Wave length

• Transverse wave 
• All electromagnetic radiation travels at the same speed in a vacuum.

1. Gamma-Rays (shortest)
2. X-rays
3. Ultraviolet
4. Visible light
5. Infra-red
6. Microwaves
7. Radio waves (longest)

• Produced by the sun and gives us sun-burn (may lead to skin cancer and damage eyes)
• Also produced by very hot gasses and fluorescent lamps.
• UV watermarks put on important documents for security. Invisible ink absorbs ultraviolet and emits visible.
• Can be used as a genetic marker
• Insects see in the UV spectrum
• Used in washing powder

• Produced by the sun and other really hot objects (filament lamps, Bunsen burners)
• Used to see things
• Can damage your eyes
• Used in photography, lasers and fibre optics.

• Comes from warm objects
• Maps the dust between stars
• Used to see at night
• Used i remote controls
• Used in burglar alarms and remotes controls

• A magnetron is a tube that uses electric and magnetic waves and changes them into intense heat
• A klystron is what produces microwaves
• They are also used in mobile phones

• Transport information through the atmosphere.
• Really long
• Used in communication
• Produced by alternating currents.
• The lowest Radio Waves are audible (ELF, SLF, ULF, VLF)

• X-rays and Gamma-rays are absorbed by dense material such as bone and metal.
• They damage living tissue when they pass through it.

They wear a film badge.

The ionosphere is a part of the atmosphere that is particularly useful for communication. This is because it can reflect some signals back to earth.

• Continuous signal
• Varies continuously in amplitude or frequency
• More interference
• Less information can be sent
• Hear noise and crackle when sent over long distances.

• Signal breaks everything into numbers
• A sequence of pulses
• Less interference. Regenerator circuits are used to clean 'noisy' pulses. Therefore higher quality.
• Digital pulses are very short so more can be carried per second.
• Maintains quality even when sent over long distances. Noise is still picked up but electronics in amplifiers are able to ignore the noise (so it doesn't get passed along).

Samples are taken and their height is converted to a series of pulses.