question_answer

Two tuning forks A and B give 4 beats per second. The frequency of A is 256 Hz. On loading B slightly, we get 5 beats in 2 seconds. The frequency of B after loading is [Haryana CEE 1996]

A)            253.5 Hz                                 

B)            258.5 Hz

C)            260 Hz                                     

D)            252 Hz

Correct Answer: C

Solution :

                   nA = Known frequency = 256 Hz, nB = ? x = 4 beats per sec which is decreasing (4 bps to                                                                                                                  ) after loading (i.e. x¯) Unknown tuning fork B, is loaded so nB¯ Hence  nA ? nB¯  = x¯        ... (i)                Wrong             nB¯  ? nA = x¯        ... (ii)               Correct Þ nB = nA + x = 256 + 4 = 260 Hz.