Question

When two tuning fork $A$ and $B$ are sounded together then $x$ beats per second are heard. The frequency of $A$ is $n$. When one of the prongs of the fork $A$ is loaded with a little wax then the number of beats decreases. The frequency of the fork $B$ is

• A. $n+x$
• B. $n-x$
• C. $n-2x$
• D. cannot be predicted

Answer 1

Answer: (B)

$n-x$

Let, n' be the frequency of fork B.

The number of beats is: $n-n^{\prime }=x$

Now, one of the prongs of the fork A is loaded with a little wax hence its frequency decrease also the number of beats decreases say to x'.

Since, number of beats is the difference in frequencies of forks, the frequency of fork must reduce by x'.

$(n-x^{\prime })-n^{\prime }=(x-x^{\prime })$

$n-x^{\prime }-x+x^{\prime }=n^{\prime }$

$n^{\prime }=n-x$