question_answer

If two tuning forks A and B are sounded together, they produce 4 beats per second. A is then slightly loaded with wax, they produce 2 beats when sounded again. The frequency of A is 256. The frequency of B will be [CPMT 1976; RPET 1998]

A)            250

B)            252

C)            260

D)            262

Correct Answer: B

Solution :

           nA = Known frequency = 256 Hz, nB = ? x = 4 bps, which is decreasing after loading (i.e. x¯) also known tuning fork is loaded so nA¯ Hence nA¯ ? nB  = x¯        ... (i)               Correct              nB  ? nA¯ = x¯        ... (ii)             Wrong Þ nB = nA ? x = 256 ? 4 = 252 Hz.