Question

A bomb blast on the moon. Its sound reaches the earth
(A) after 10 minutes
(B) after 24 hours and 10 minutes
(C) after 3.7 minutes
(D) cannot reach

Answer 1

In this question we are going to apply the concept of propagation of sound waves like what are the criteria required for their propagation. Sound waves are longitudinal waves and longitudinal waves require a medium to travel.

Complete step by step answer:
This question discusses the time taken by the sound to reach earth if there is a bomb blast on the moon. Now look, first we need to understand how sound travels between two points. Sound is basically a vibration which travels in the form of waves.
There are two types of waves: - Longitudinal wave and Transverse wave.

Longitudinal Waves	Transverse wave
Travel in the direction next which the vibrations are taking place.	Travels in the direction perpendicular to which the vibrations are taking place.
Require a medium for their propagation.	Require no medium for their propagation.
They are physical waves as they use particles in the medium for their movement.	They are just a form of energy which requires no medium
Examples: - Sound waves	Examples: - Heat radiation

So, from this definition of the waves it is very much clear that sound waves cannot travel in vacuum. Since we know that there is vacuum between earth and moon, no matter is present there, so any sound or in fact any vibration which originates on moon cannot escape its surface and reach earth.

Hence, option (D) is the correct answer.

Note: The fact that moon does not have any atmosphere which means that it has no medium present on its surface too, due to this no sound can ever be heard on the moon’s surface because the moment it originates, it has no medium around it to travel. The only way for us to know if there is a bomb blast on the moon is through vision. If the blast is large enough, it could be seen through a telescope.