Question

When sound travels through air, the air particles:
A. Vibrate along direction of wave propagation
B. Vibrate but not in any fixed direction
C. Vibrate perpendicular to direction of wave propagation
D. Don’t vibrate

Answer 1

The main hint to this question is that the sound waves are the longitudinal type of waves. They are called so because particles of the medium through which the sound is transported vibrate parallel to the direction that the sound wave moves.

Complete answer:
On the basis of particle motion waves are classified into two categories that are;
-Longitudinal waves
-Transverse waves
Longitudinal waves are the waves in which the vibration of the medium is parallel to the direction the wave travels and displacement of the medium is in the same or opposite direction of the wave propagation.

Transverse waves are the waves whose oscillations are perpendicular to the direction of the wave’s advance. A simple example is given by the waves that can be created on a horizontal length of string by anchoring one end and moving the other end up and down.

So, here in this question we are talking about sound waves and sound waves are longitudinal types of waves. Therefore the motion of the particles is along the direction of the wave propagation.

Hence, option A is the correct answer.

Note: Here we can add some additional information about sound waves that sound waves always require a medium to travel like solid, liquid or gas. Speed of sound is highest in solids than liquids and at last gases. Sound waves do not travel through vacuum. And also sound waves are produced when an object vibrates, by creating a pressure wave.