Wave Basics

A wave is a disturbance that transfers energy from place to place. It consists of oscillating particles in space or matter.
Waves are typically characterised by amplitude, wavelength, frequency, and speed.
The amplitude of a wave is the maximum displacement of a point from its equilibrium position. It measures the energy carried by the wave.
The wavelength is the distance over which a wave’s shape repeats. It’s the distance between consecutive points of a wave such as from crest-to-crest or trough-to-trough.
Frequency, measured in hertz (Hz), is the number of waves passing a point in a unit of time. It’s the inverse of the period of a wave.
The speed of a wave is calculated as the product of its wavelength and frequency.
Waves can be classified as transverse or longitudinal.
Transverse waves are those where the oscillations are perpendicular to the direction of energy transfer. Examples include light waves and waves on a string.
Longitudinal waves are those where the oscillations are parallel to the direction of energy transfer. Sound waves in air are longitudinal waves.
Another property of waves is polarisation which can only be demonstrated by transverse waves. It refers to the orientation of the oscillations in a transverse wave.

When waves encounter a boundary between two different media, they can be reflected, transmitted, or absorbed.
Reflection happens when a wave bounces off a surface. The law of reflection states that the angle of incidence is equal to the angle of reflection.
Transmission is when the wave travels through a boundary into another medium or continues to travel through the original medium. During transmission, waves often undergo a change in speed and direction which is known as refraction.
Absorption is when a medium converts the energy in a wave into other forms, typically heat. This reduces the amplitude of the wave.
Waves can also interfere with each other, creating resultant waveforms. When two waves meet in phase (peaks to peaks, troughs to troughs), they create constructive interference leading to a higher amplitude. When they meet out of phase, they create destructive interference, reducing the overall amplitude.