Question

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

(a) 286cps 

(b) 292cps

(c) 294cps 

(d) 288cps.

Answer 1

(b) : The wax decreases the frequency of unknown fork. The possible unknown frequencies are (288 + 4)cps and (288 – 4)cps.

Wax reduces 284cps and so beats should increases. It is not given in the question. This frequency is ruled out. Wax reduced 292cps and so beats should decrease. It is given that the beats decrease to 2 from 4. Hence unknown fork has frequency 292cps.