question_answer

A tuning fork A of frequency 200 Hz is sounded with fork B, the number of beats per second is 5. By putting some wax on A, the number of beats increases to 8. The frequency of fork B is                                       [MP PMT 1996]

A)            200 Hz                                     

B)            195 Hz

C)            192 Hz                                     

D)            205 Hz

Correct Answer: D

Solution :

                   nA¯ ? nB = x­         ... (i)                Wrong nB  ? nA¯ = x­        ... (ii)               Correct Þ nB = nA + x = 200 + 5 = 205 Hz.