sound

1. Wave: wave is a kind of disturbance which propagates through a medium due to the repeated oscillatory motion of the particles of the medium about their mean positions ,the motion being handed over from one particle of the medium to the next particle progressively.
2. Wave  can be of two  types on the basis of medium requirement.These are Mechanical waves & electromagnetic waves.

• Mechanical waves/Elastic waves: mechanical wave is the disturbance takes place in a material medium for its propagation .sound waves,water waves,waves in spring & on ropes  are mechanical waves.
• Electromagnetic waves:  electromagnetic waves are waves which do not need any medium for their propagation. light waves can pass through vacuum.eg radio waves,micro waves,gamma rays, ultraviolet rays,X-rays ,etc.

1. Wave can be of two types on the basis of propagation in a medium:

• Transverse wave:.  A wave in which particles of the medium move up and down perpendicular to the the direction of the wave propagation in the medium is known as transverse wave .It can propagate through solids & on the surfaces of liquids. A wave Travels in the form of crests and troughs.Eg.light wave,
• Longitudinal wave: A wave in which particles of the medium move to and fro about their mean positions along the direction of propagation of the wave is called the longitudinal wave such a wave travels in the the form of compression and rare factions.It can propagate freely through solids,liquids & gases.Eg sound wave,