Question

Two tuning forks $A$ and $B$ vibrating simultaneously produce $5$ beats. Frequency of $B$ is $512Hz$. It is seen that if one arm of $A$ is filed, then the number of beats increases. The frequency of $A$ will be

• A. 502 Hz
• B. 507 Hz
• C. 517 Hz
• D. 522 Hz

Answer 1

Answer: (C)

There are five beats between $A$ and $B$, therefore, the possible frequencies of $A$ are
$512\pm 5=(517$ or $507)Hz$
When one prong of $A$ is filed its frequency becomes greater than the original frequency. If we assume that the original frequency of $A$ is $517Hz$, then on filing its frequency will be greater than $517Hz$. The beats between $A$ and $B$ will be more than $5.$ But it is given that the beats are increasing so it is only possible if frequency of $A$ is $517Hz$