Question

Which statement is true,

Statement 1: Sound needs a medium for its propagation

Statement 2: Sound does not propagate in a vacuum, as it does not have particles to vibrate.

Answer 1

Explanation for statement 1:

1. A sound is a form of energy and it travels in the form of waves.
2. This energy travels through the vibrations of the particles in the medium.
3. This is the reason why the speed of sound is different for different mediums because it depends on the density of the medium.
4. The denser the medium, the more will be the particle vibration and the greater will be the speed of sound.
5. Therefore, the given statement is true.

Explanation for statement 2:

1. Sound cannot travel in a vacuum because it needs a medium to propagate.
2. Sound travels through particle vibrations but there are no particles in a vacuum.
3. This can be easily demonstrated by the bell-jar experiment in which an electric bell is placed in a sealed jar and the air from the jar is slowly excavated.
4. A person can clearly hear the bell sound at first but as the air is slowly excavated, the intensity of the sound gradually decreases and when there is no air inside the container, no sound can be heard.
5. Therefore, the given statement is true.

Hence, both statement 1 and statement 2 are true.