Question

The frequency of tuning fork A is 2% more than the frequency of a standard fork. Frequency of tuning fork B is 3% less than the frequency of the standard fork. If 6 beats per second are heard when the two forks A and B are excited, then frequency of A is……….Hz. 

(A) 120 

(B) 122.4 

(C) 116.4 

(D) 130

Answer 1

The correct option (B) 122.4

Explanation:

Let frequency of standard fork = x

 f_A = {(102)/(100)} x

 f_B = {97/(100)}x

f_A – f_B = {(102x)/(100)} – {(97x)/(100)} = {5x/(100)}

given  f_A – f_B = 6

∴ (x/20) 6

∴ x = 120Hz

f_A = {(102)/(100)} × 120

f_A = 122.4Hz