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 the original frequency of tuning fork A i s ______ Hz.
Physics · Wave Motion · beat and properties of sound like loudness,pitch
JEE Mains 2026 28 January Evening Shift

Question

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 the original frequency of tuning fork A i s ______ Hz.

Physics · Wave Motion · beat and properties of sound like loudness,pitch

JEE Mains 2026 28 January Evening Shift

G1 Physics · Accepted Answer

Initially, 8 beats in 2 s means beat frequency f(beat) = 8/2 = 4 Hz. Therefore, |f(A)-f(B)| = 4. Given, f(B) = 380 Hz. Thus, f(A) = 384 Hz or 376 Hz. When wax is loaded on fork A, its frequency decreases. The new beat frequency is 4 beats in 2 s = 2 Hz. If the original frequency were 376 Hz, loading wax would decrease it further below 376 Hz and the difference from 380 Hz would increase, not decrease. Therefore the original frequency must be f(A) = 384 Hz. Hence the answer is 384.