Question

Complete the following sentence.
Sound cannot travel through _____, but it requires a _____.
(A) Air, medium
(B) Water, medium
(C) Solids, medium
(D) Vacuum, medium

Answer 1

Sound waves are the type of mechanical waves, which can only travel if a medium is available. You cannot hear the explosion on the moon. Speed of sound is highest in a medium in which molecules are tightly packed.

Complete answer:
- Let us discuss something about sound which is a form of wave. Sound waves require a medium such as a solid, liquid, or gas to pass through. By vibrating the molecules in the matter, the sound waves pass through each one of these mediums. In solids, the molecules are very closely packed. Liquids, including solids, are not packed as closely. And the gases are packed very loosely. The molecules' spacing allows sound to move through a solid even faster than a gas. Sound flows in water nearly four times quicker and deeper than it does in air.Sound waves are particle motions in media such as air, water or metal that move. It is also logical that they are unable to move across empty space, where no atoms or molecules can vibrate.
-Let us discuss an interesting fact. In vacuum, sound does not move at all. The deep space vacuum has virtually zero air. Since sound is only air vibration, there is no air to vibrate in vacuum, so there is no sound. You wouldn't hear it if you were alone on a rocket ship and another space ship detonated.Hence, from the above discussion it can be concluded that sound cannot travel through vacuum, but it requires a medium.

The correct option is D.

Note: While answering this question, most of the students are generally seen to make common mistakes by some misconception that sound cannot travel through solids and they think that the sound is perfectly blocked by solids. Rather, the speed of sound is highest in solids. However, if you enclose a source of sound inside a metal, then you may not hear the sound. This is a different case.