Question

When a tuning fork $A$ of unknown frequency is sounded with another tuning fork $B$ of frequency $256Hz$, then $3$ beats per second are observed. After that $A$ is loaded with wax and sounded, the again $3$ beats per second are observed. The frequency of the tuning fork $A$ is

• A. $250Hz$
• B. $262Hz$
• C. $259Hz$
• D. $253Hz$

Answer 1

The correct option is C $259Hz$

Given, known frequency of $B$ is,
$N_B=256Hz$.

$N_B$ produces $3$ beats per second with $N_A$. After that $A$ is loaded with wax and sounded, the again $3$ beats per second are observed.

$x=3bps$ (Which remains the same after loading).

Frequency of $A=$?

When the unknown tuning fork $\left(A\right)$ is loaded with wax, the frequency $\left(N_A\right)$ is decreasing. But both the $N_B$ and $x$ are not changed when loaded. Hence,

$N_A-N_B=x$
$N_A=N_B+x$
$N_A=256+3$
$N_A=259Hz$

Final Answer: (c)