Question

In wave motion the particles of the medium:
A. Remain fixed
B. Vibrate to and fro about their mean position
C. Move along the wave
D. Change their positions permanently

Answer 1

Hint:The sound waves are produced by a vibrating body. The vibrating mass travels in one direction and compresses the air immediately in front of the mass. As the vibrating object travels in the opposite direction, the pressure on the air is minimised in such a manner that the expansion or rarefaction of the air molecules happens.

Complete answer:
Sound Production of vibrating objects in a tuning fork. The fork is made up of two tines and a handle. When a rubber hammer strikes, the two tines appear to vibrate. The back and forth motion of the tines creates disturbances in the ambient air molecules. When the tines spread out from their original location, they compress the surrounding air molecules and result in the formation of a high-pressure area close to the tine.

As the tine moves inward, it creates a low-pressure area near the tine. With more tine vibrations, an alternating pattern of high and low-pressure regions is formed. These pressure differential regions help to disperse sound waves from one location to another.

The sound produced is conveyed by the pressure waves within the material. An object that vibrates back and forth easily forces air out to make room for itself. As a force is applied on an atom, it shifts from its original location and exerts force on the opposite atom. This transition from one particle to another continues in the medium. In this way, the sound is conveyed via a medium.

Thus from the above discussion we can say that in wave motion the particles of the medium vibrate to and fro about their mean position.

Hence, option B is correct.

Note:A wave is a disturbance in a medium that carries energy without a net movement of particles. It may take the form of elastic deformation, a variation of pressure, electric or magnetic intensity, electric potential, or temperature.A wave in which the medium particles oscillate to and fro around their mean location in the direction of propagation is known as the longitudinal wave. Sound waves are longitudinal waves.