Physics

(B) On the Basis of mode of Vibration of the Particle
TRANSVERSE WAVES
A wave in which the particles of the medium oscillate about their mean position in a direction perpendicular to the direction of propagation of the wave is called a transverse wave.
Transverse waves can travel through solids and over the surface of liquids, but not through gases.
Examples : Following are the examples of transverse waves :
(i) The water waves (ripples) produced on the surface of water is transverse waves. In water waves, the molecules of water move up and down from their mean positions.
(ii) A pulse on a slinky when it is given a jerk is a transverse wave.
(iii) All electromagnetic waves, e.g., light waves, radio waves etc., are transverse waves.
(iv) The waves produced in a stretched string when plucked are transverse waves. When a string of sitar (a musical instrument) or guitar is plucked, transverse waves are produced in the string.

Graphical Representation :

(a) Crest : The highest point on the hump in a transverse wave is called a crest. Thus, the point of maximum positive displacement on a transverse wave is called a crest.
(b) Trough :The lowest point on the depression in a transverse wave is called a trough. Thus, the point of maximum negative displacement on a transverse wave is called a trough.
LONGITUDINAL WAVES :
A wave in which the particle of the medium oscillate (vibrate) to and fro about their mean position in the direction of propagation of the wave is called a longitudinal wave.
Longitudinal waves can be produced in any medium, viz., in solids, liquids and in gases.
Example :
(i) Sound waves are longitudinal waves.
(ii) The waves produced in a spring (slinky) by compressing a small portion of it and releasing are longitudinal waves.
Graphical Representation :

(a) Compression : The part of a longitudinal wave in which the density of the particles of the medium is higher than the normal density is called a compression.
(b) Rarefaction : The part of a longitudinal wave in which the density of the particles of the medium is lesser than the normal density is called a rarefaction.