Question

Two tuning forks A and B vibrating simultaneously produce 5 beats. Frequency of B is 512. It is seen that if one arm of A is filed, then the number of beats increases. Frequency of A will be

• A. 502
• B. 507
• C. 517
• D. 522

Answer 1

Answer: (C)

517

Answer 2

After filling frequency increases, so $n_{A}$ decreases (↓). Also it is given that beat frequency increases

(i.e., x ↑)

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

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

⇒ n_A = n_B + x = 512 + 5 = 517 Hz.