Question

When longitudinal wave propagates through a medium, then the physical quantities propagating in the direction of wave are:
A) Energy
B) Energy, momentum and mass
C) Energy and mass
D) Energy and momentum

Answer 1

Hint: When a wave is produced by disturbance of medium, it is transported with the help of oscillating particles of the medium. The oscillation is a type of energy which is transferred from one part to another. Therefore only energy propagates with the propagation of longitudinal waves. If the particle travels with the wave then it is considered as particle flow.

Complete answer:
When a longitudinal wave propagates through a medium then energy also propagates with the wave. Generally wave is the periodic oscillation of the particles of a medium in their mean positions. So they do not require the flow of particles or masses. The wave is transported through the regular disturbances which carry energies with them. Other than this momentum and mass cannot travel with the wave. Then the wave is considered as particle flow.

There are generally two types of waves: longitudinal and transverse waves. In transverse waves propagation of waves is perpendicular to the cause of disturbance. For ex- when a stone is dropped inside a still lake, the wave produced is tangential to the surface and motion of stone is perpendicular to it. And a longitudinal wave is a wave in which the cause of disturbance and wave is in the same direction. For ex- motion of a moving earthworm. In waves particles carry energy with them. The general term of energy in a wave is given by planck's energy equation i.e. $$E=h\upsilon$$.

Note: Generally waves do not carry particles with them and bigger particles cannot perform wave motion due to its mass. So the wave produced by disturbance of the medium carries energy which generates further wavelets. Secondary waves are produced by initial waves which carry enough energy to produce further waves.