Figure below shows two tuning forks A and B of the same frequency mounted on two separate sound boxes with their open ends facing each other. The fork A is set into vibration. (a) Describe your observation. (b) State the principle illustrated by this experiment.

(a) During the above experiment, we observe that,

When the prong of one of the tuning forks say, A is struck on a rubber pad, it starts vibrating. On putting the tunning fork A on its sound box, we find that the other tuning fork B also starts vibrating and a loud sound is heard.

The vibrating tuning fork A produces the forced vibration in the air column of its sound box. These vibrations are of large amplitude because of large surface area of air in the sound box.

These vibrations are communicated to the sound box of the fork B. The air column of B starts vibrating with the frequency of fork A. Since the frequency of these vibrations is same as the natural frequency of the fork B, the fork B picks up these vibrations under resonance.

(b) The principle illustrated by the above experiment is Resonance.