Question

Two tuning forks P and Q are vibrated together. The number of beats produced are represented by the straight line OA in the following graph. After loading Q with wax again these are vibrated together and the beats produced are represented by the line OB. If the frequency of P is 341 Hz, the frequency of Q will be:

• A. 341 Hz
• B. 338 Hz
• C. 344 Hz
• D. 330 Hz

Answer 1

The correct option is C 344 Hz

Given: Frequency of P ${\nu }_P=341Hz$

We can see from graph that before loading the Q with wax, beat frequency (number of beats in one second) is $\nu =3Hz$.

Hence frequency of Q ${\nu }_Q=341\pm 3=344or338Hz$,

Now if frequency of Q is 338Hz , on loading the Q with wax, is frequency decreases and beat frequency should increase but it is clear from the graph that beat frequency is decreasing (shown by graph B), therefore frequency of Q is not 338Hz but 344Hz.