Question

A bomb blasts on the moon. Its sound will be heard on earth after
A) $3.7$minutes
B) 10 minutes
C) 138 minutes
D) Sound will never be heard

Answer 1

Hint
Electromagnetic waves like light do not need a medium to travel. They can travel not only through air and solid materials, but also through the vacuum of space. However, the same is not true for mechanical waves.

Complete step by step answer
A wave is a disturbance or variation that travels from point to point in a medium. Electromagnetic waves are created due to the interference between vibrations produced by electric and magnetic fields simultaneously. The two fields act in directions perpendicular to each other. These waves do not require a medium to travel. Common examples of electromagnetic waves include light, ultraviolet radiation from the Sun, etc.
Mechanical waves travel through a medium at a speed which depends on the elastic and inertial properties of that medium. They transfer their energy as they propagate. As these waves rely on particle interaction in order to transport their energy, they cannot travel through regions of space that are void of particles. Sound is a widely known mechanical wave.
We know that outer space is devoid of any matter, and the moon lies far beyond the Earth’s atmosphere. If a bomb were to blast on the moon, the sound waves generated from it would not be able to travel through space, and hence, we will not hear anything.
Hence the correct answer is option (D).

Note
Sound needs a material medium to travel is easily demonstrated by the electric bell jar experiment. In this, an electric bell is placed in a jar sealed at the top. As the air is slowly pumped out of the jar, the sound of the bell begins to fade to an outside listener. When a perfect vacuum is achieved inside the jar, no sound is heard outside.