Q.

In a guitar, two strings A and B made of same material are slightly out of tune and produce beats of frequency 6 Hz. When tension in B is slightly decreased, the beat frequency increases to 7 Hz. If the frequency of A is 530 Hz, the original frequency of B will be          [2020]

1 523 Hz  
2 524 Hz  
3 536 Hz  
4 537 Hz  

Ans.

(2)

Frequency of string A, υA=530 Hz and beat frequency Δυ1=6 Hz.

Since, υB=υA±Δυ1, we have υB=536 Hz or 524 Hz

Now, when tension on the string is reduced, its frequency reduces.

Now, the beat frequency, Δu2=7Hz

   The original frequency of B, υB=524Hz