Question

In fig. , P, Q, R and S represent test tubes each of height 20 cm which are filled with water upto heights of 10 cm, 14 cm, 16 cm and 18 cm respectively. If a vibrating tuning fork is placed over the mouth of test tube Q, a loud sound is heard.
(i) Describe the observations with the tubes P, R and S.
(ii) Give the reason for your observation in each case.
(iii) State the principle illustrated by the above experiment.

Answer 1

(i) No loud sound is heard with P and R but a loud sound is heard with S.
(ii) Resonance occurs with the air column in tubes Q and S whereas no resonance occurs in the air columns of tubes P and R. The frequency of vibrations of air column in the tube S is thrice the frequency of vibrations of air column in the tube Q, while the frequency of vibrations of air column in tubes P and R is neither equal to nor an integer multiple of frequency of vibrations of air column in tube Q.
(iii) When the frequency of vibrations of air column is either equal to or an integer multiple of the frequency of the vibrating tuning fork, resonance occurs.