Travelling Waves

A travelling wave is a wave in which the points of identical phase (like the crests or troughs) appear to move in one direction.
The motion of travelling waves is usually instigated by a disturbance or oscillation at one location within a medium or field.
The energy of a travelling wave moves from one point to another, this is known as the wave’s energy transmission.

Wave Properties

The wavelength (λ) describes the spatial period of the wave, it is the distance over which the wave’s shape repeats.
The peak or crest of a wave is the maximum value of displacement within a wave cycle. The trough is the minimum displacement value.
The amplitude (A) of a wave is the maximum displacement from the equilibrium position which is often the wave’s mid-point.
Frequency (f) is the number of complete cycles (oscillations or waves) per unit time. It is measured in Hertz (Hz).

The wave speed (v) is calculated as the product of wavelength (λ) and frequency (f), that is v = fλ. It represents how fast a point on the wave moves through space.
The point where a wave oscillates around is referred to as the equilibrium position. When a wave is travelling, energy is transmitted from the source but the medium through which it passes ideally returns to its equilibrium position when the wave has passed.
The energy of a wave is proportional to the square of its amplitude. Double the amplitude, and you quadruple the energy.

Mechanical waves, such as sound waves and water waves, require a medium (like air or water) to travel through and cannot travel through a vacuum.
Electromagnetic waves, like light and radio waves, can travel through space and do not require a medium.
A pulse wave or wave pulse is a single non-periodic disturbance while a periodic wave repeats with a specific frequency.

When two waves meet while they are travelling, the principle of superposition applies. This states that the total displacement is the vector sum of the displacements of the individual waves.
When waves meet and their peaks line up, this results in a bigger wave, a phenomenon called constructive interference.
When a peak of one wave lines up with a trough from another, they can cancel each other out leading to a smaller resultant wave or flat line in case of complete cancellation. This is known as destructive interference.