Question

A sound wave is generated by the howl of a wolf in the night. How would we describe the motion of a particular air molecule near the ground, a mile away from the wolf, on average (i.e. ignoring the random wandering of gas molecules)?
A. it moves back and forth (oscillating) towards the wolf.
B. it moves in the horizontal circle.
C. it moves up and down in an oscillating fashion.
D. it moves away from the wolf at the speed of sound.

Answer 1

Hint: We know that a sound is caused due to the vibrations of the particles in a medium. We are able to perceive sound when these vibrations reach our ears and cause our eardrums to vibrate. Also the vocal cords are needed to produce sounds.

Complete step by step answer:
We know that sound waves are longitudinal waves which need a medium to get transferred or propagated. The to and fro motion of the particles in the medium helps in the propagation of these waves.
Thus here, the howl of the wolf travels through the air. The propagation of the howl causes oscillation of the air particles.
Hence the answer is A. it moves back and forth (oscillating) towards the wolf.
Additional information:
A sound wave is a longitudinal 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. Thus 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.

Note:
We humans can perceive sound whose frequency is of the range $20-20kHz$. 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.