Question

A bomb explodes on the moon. How long will it take for the sound to reach the earth?
A. \[1\] day
B. \[1000\,{\text{s}}\]
C. \[10\,{\text{s}}\]
D. None of these.

Answer 1

Hint: First recall the definition of sound which states that a sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. The Moon is in space, and space is mostly a vacuum, thus there is no sound on the Moon.

Complete step by step solution:
Here,
From the definition of sound we know that,
Sound waves are mechanical waves that need an elastic medium to propagate. In the space between the moon and the earth there is no medium (solid, liquid or gas). Sound is created in the medium particle due to vibrations, that is, it requires some medium for propagation and the moon has no atmosphere.

Therefore, one will never listen to the sound of the blast occurring on the moon. So ultimately, no medium for propagation of waves or vibrations of a medium particle will occur.
Hence, the correct answer is (D) none of these.

Note: Sound is a mechanical wave which results from the vibration back and forth of the media particles through which the sound wave travels. Particle motion is parallel (and anti-parallel) to the energy transport direction. That is what characterises the longitudinal waves of sound in air.
Sound medium is a material that moves sound waves in. Air for instance is a medium of sound. A characteristic of musical sounds is the consistency of tone, also called timbre. Air does not need to be the medium; metal, wood, stone, glass, water and many other substances do sound, many of them better than air.