Question

A tuning fork of unknown frequency makes three beats per second with a standard fork of frequency 384 Hz. The beat frequency decreases when a small piece of wax is put on a prong of the first fork. What is the frequency of this fork ? (in Hz)

Answer 1

$answer:387Hz$

$beats=|f_1-f_2|$

since on adding wax to unknown tuning fork the frequency $f_1$ reduced

and also beats reduced this means that $f_1>f_2$

$f_1-384=3$

$f_1=387Hz$