Question

When two tuning forks $A$ and $B$ are sounded together. $4$ beats per second are heard. The frequency of the fork $B$ is $384\, Hz$. When one of the prongs of the fork $A$ is filed and sounded with $B$. the beat frequency increases, then the frequency of the fork $A$ is

• A. 380 Hz
• B. 388 Hz
• C. 379 Hz
• D. 389 Hz

Answer 1

Answer: (B)

Given, frequency of fork $B$,
$v_{B}=384 \,Hz$
We know that,
$v_{A}-v_{B}= 4 $
$v_{A}-384=4 $
$ v_{A}=384+4$
Frequency of fork $A$,
$v _{ A }=388 \,Hz$