question_answer

A tuning fork sounded together with a tuning fork of frequency 256 emits two beats. On loading the tuning fork of frequency 256, the number of beats heard are 1 per second. The frequency of tuning fork is [NCERT 1975, 81; MP PET 1985]

A)            257

B)            258

C)            256

D)            254

Correct Answer: D

Solution :

           nA = Known frequency = 256, nB = ? x = 2 bps, which is decreasing after loading (i.e. x¯) known tuning fork is loaded so nA¯ Hence nA¯ ? nB = x¯        ... (i)   Correct              nB  ? nA¯ = x¯      ... (ii)              Wrong Þ nB = nA ? x = 256 ? 2 = 254 Hz.