Waves: Units

Key Principles of Waves

Waves transport energy from one place to another without the need for matter to be moved.
Waves can be classified into two main types: transverse waves and longitudinal waves.
In transverse waves, particles vibrate at right angles to the direction of the wave (like on the ocean’s surface). In longitudinal waves, particles vibrate in the same direction as the wave (like sound waves).

Each wave has several properties: wavelength, frequency, amplitude and wave speed.
The wavelength is the distance between two consecutive points in a wave that are in phase like from crest to crest or trough to trough. The unit of wavelength is metres (m).
Frequency indicates the number of waves produced by a source each second. It’s measured in hertz (Hz).
The amplitude of a wave is the maximum displacement of the particles in the wave from their equilibrium position. Its unit is also metres (m).
The wave speed (or wave velocity) is the speed at which the wave moves in a particular direction. Wave speed is measured in metres per second (m/s).

The wave speed, frequency and wavelength of a wave are related by the equation v = f λ (wave speed = frequency × wavelength).

Waves can demonstrate several behaviours when interacting with matter or other waves. These interactions include reflection, refraction, diffraction and interference.
Reflection is when the wave bounces back from a barrier.
Refraction is the bending of waves due to a change in speed when moving from one medium to another.
Diffraction is the spreading out of waves around obstacles or through gaps.
Interference is when two waves superpose to form a resultant wave of greater, lower, or the same amplitude.

The electromagnetic spectrum is a family of waves that includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
All types of electromagnetic waves travel at the same speed in vacuum, which is the speed of light, 3.0 x 10^8 m/s.
They differ in their frequencies and wavelengths.
The highest frequency and shortest wavelength electromagnetic waves are gamma rays, while the lowest frequency and longest wavelength waves are radio waves.