Q 11-14-034JEE MainJEE Main 2026 (28 Jan, Shift 2)Easy
Two tuning forks $A$ and $B$ are sounded together giving rise to 8 beats in 2 s. When fork $A$ is loaded with wax, the beat frequency is reduced to 4 beats in 2 s. If the original frequency of tuning fork $B$ is 380 Hz then original frequency of tuning fork $A$ is ______ Hz.
Numerical value type. Enter your answer.
Answer: 384
Beat frequency initially: $8/2 = 4$ Hz, so $f_A = 380\pm4 = 384$ or $376$ Hz.
Loading $A$ with wax lowers $f_A$. The beat frequency then falls to $4/2 = 2$ Hz, which can happen only if $f_A$ was **above** $f_B$ (lowering it brings it closer to 380 Hz).
So $f_A = 384$ Hz.
Solution by Sreeraj P, M.Sc Physics