question_answer

Two tuning forks A and B vibrating simultaneously produce 5 beats. Frequency of B is 512. It is seen that if one arm of A is filed, then the number of beats increases. Frequency of A will be                                     [MP PMT 1991]

A)            502

B)            507

C)            517

D)            522

Correct Answer: C

Solution :

           After filling frequency increases, so \[{{n}_{A}}\] decreases (¯). Also it is given that beat frequency increases (i.e., x ­)  Hence nA¯ ? nB  = x­        ... (i)               Correct             nB  ? nA­ = x­        ... (ii)              Wrong Þ nA = nB + x = 512 + 5 = 517 Hz.