Wave

• Waves propagate through a medium as atoms and molecules bump into each other producing a domino affect.
• Waves share common features such as amplitude, crests, direction of travel, frequency and wavelength.

About waves in water

• If you throw a stone into a pond it produces a series of ripples (waves) that spread out in concentric circles before crashing against obstacles.
• Seen from a boat at sea, waves form as the wind and tide apply forces that disturb the water.
• In general terms:
  • The frequency of waves in water can be counted as individual waves rise to a crest at any given point.
  • Wavelength can be calculated by looking at the distance from the crest of one wave to the crest of the next.
  • Amplitude can be measured by looking at the distance from the top of a crest of a wave to the bottom of the next trough.
  • When looking at waves on water it is easy to see in what direction they are travelling.
  • The energy carried by waves at the beach is obvious when you go for a swim and are thrown head-over-heels.

Electromagnetic waves

• Electromagnetic waves are invisible either because they are too small to see or because our eyes don’t respond to them:
  • The wavelength of some radio waves can be measured in metres but our eyes are not tuned to see them.
  • When we see colours around us electromagnetic waves are entering our eyes but their amplitude, frequency and wavelength are too small to see.
  • Whilst we may not be able to see electromagnetic waves we may be able to sense them as heat or feel a buzz in a wire.
• Electromagnetic waves can vary in size so much that their wavelength may need to be measured in kilometres or trillions of picometres (10¹²) .
• The frequency of electromagnetic waves may be as infrequent as 1 per second (1 hz per second) or as frequent as a quadrillion per second (10¹⁵).