Question

Sound travels in air if
A. Particles of medium travel from one place to another
B. There is no moisture in the atmosphere
C. Disturbance moves
D. Both particles as well as disturbance travel from one place to another

Answer 1

Sound wave is a mechanical wave. The disturbance which travels through a material medium, due to collective vibration of the particles of the medium is called mechanical waves.

Complete step by step answer:
Wave is a disturbance that travels through a medium, whereas particles constituting the medium do not travel. We are familiar with different types of waves like sound waves, light waves, radio waves etc.
There is a special type of wave called Mechanical Wave which can only propagate through material medium, these can’t propagate through vacuum.
Cohesion: The adjacent molecules of material medium can attract each other. This phenomenon is known as cohesion. The origin and propagation of Mechanical Waves depends upon
Elasticity: If any part of a material or a medium is displaced from its equilibrium position, a stress is developed in it due to elasticity. This stress tries to bring the part back to its original position.
Inertia: When a particle returns to its equilibrium position, it has a motion due to inertia. So, the particle can’t come to rest immediately on reaching equilibrium position. Due to inertia of motion, it moves opposite side crossing the equilibrium position.
Sound wave is a mechanical wave. In the material medium where sound waves propagate, each particle of the medium forces adjacent particles to vibrate, but the particle itself is not carried away from its equilibrium position; rather, the wave advances through the medium.
So, the correct answer is (C) Disturbance moves.

Note: Elasticity of a medium has no relation with electric and magnetic fields. So, electromagnetic waves like light waves, radio waves etc. are not mechanical waves. So, they can travel through vacuum as well as through solid, liquid or gas.