Question

A tuning fork arrangement (pair) produces $4$ beats/s with one fork of frequency $288$ cps. A little wax is placed on the unknown fork and it then produces $2$ beats/s. The frequency of the unknown fork is:

• A. 286 Hz
• B. 292 Hz
• C. 294 Hz
• D. 288 Hz

Answer 1

The correct option is B 292 Hz

Let the frequency of the unknown fork be $v$.

As It produces, $4$ beats with $288Hz$,

$\Rightarrow |v-288|=4$

$\Rightarrow v-288=\pm 4\Rightarrow v=292$ or $284Hz$

waxing of fork decreases its frequency.

Since, beat frequency also drops, the frequency of unknown fork has to be, $v=292Hz$.