Question

When a tuning fork A of unknown frequency is sounded with another tuning fork B of frequency 256 Hz, 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. 250 Hz
• B. 253 Hz
• C. 259 Hz
• D. 262 Hz

Answer 1

Answer: (C)

259 Hz

Answer 2

It is given that

n_A = Unknown frequency = ?

n_B = Known frequency = 256 Hz

x = 3 bps, which remains same after loading

Unknown tuning fork A is loaded so n_A↓

Hence n_A↓ – n_B = x ... (i) $\longrightarrow$ Correct

n_B – n_A↓ = x ... (ii) $\longrightarrow$ Wrong

⇒ n_A = n_B + x = 256 + 3 = 259 Hz.