Previous Year Question

Sound is a Mechanical Wave. A mechanical wave requires a material medium for its propagation. This medium may be a solid, liquid or gas.

When an object vibrates, it makes the particles of the surrounding medium vibrate. These particles transfer the disturbance to neighbouring particles, and in this way sound energy propagates forward.

Therefore, sound can travel through solids, liquids and gases, because particles are present in all these media.

However, a Vacuum contains no material particles, so there is no medium through which vibrations can be transferred from one particle to another. Hence, sound waves cannot propagate through a vacuum.

For the same reason, if there is no material medium between two astronauts in space, they cannot hear each other merely by speaking directly; communication requires radio or electromagnetic waves.