Question

A sound wave travels from west-east; in which direction do the particles of the air move?
A. west-east
B. south-north
C. up-down
D. none of these

Answer 1

Hint: We know that sound waves are both transverse and longitudinal waves. Also, the sound waves are caused due to the vibrations or oscillation of the particles of the sound wave in any given medium. The nature of propagation of sound waves depends on the medium.

Complete answer:
Sound is transferred as longitudinal waves in fluids. We also know that these particles in the sound waves travel in the direction of propagation of the sound.
Here, it is given that the wave travels in from west to east, and the medium here is air, which is a gas. Then the propagation of the particle must also be in the direction of the wave, which is from west to east.

Thus the answer is option A. west-east

Additional information:
The speed of the light is interdependent of the medium, whereas the sound of the medium is dependent on the medium through which it propagates. This is the reason why during a thunder, we see the lighting striking first and later the sound of the thunder is heard.
We humans can perceive sound whose frequency is of the range \[2020kHz\]. Anything above or below this range our ears cannot perceive them. Any sound above \[20kHz\] is called ultrasound which is used by bats and whales for communications. And sounds below \[20Hz\] are called infrasound.

Note:
A sound wave is both longitudinal and transversal wave which needs a medium to propagate. The propagation of sound is due to rarefaction and compression of the waves. Whereas light waves are transverse waves, which don’t need a medium to propagate.