As the pulse in figure travels, each disturbed element of the string moves in a direction perpendicular to the direction of propagation. Figure illustrates this point for one particular element, labelled P. Notice that no part of the string ever moves in the direction of the propagation. A travelling wave or pulse that causes the elements of the disturbed medium to move perpendicular to the direction of propagation is called a transverse wave.
For transverse wave propagating in a taut string. When the displacement of a particle is maximum above the line of mean position, the particle is said to be at crest of the wave, and when the displacement of a particle is maximum below the mean position it is said to be at the trough of the wave.
A particle either at the crest or at the trough has a tendency to move towards the mean position.
- A particle at the crest or the trough has zero velocity, and the distance of the particle from the mean position is termed as amplitude of the wave.
- Distance between two consecutive crests/troughs is equal to the wavelength of the wave.
Distance between a consecutive pair of crest and trough is half the wavelength of the wave.