The correct option is (C) 280 (cm / s).
Explanation:
f = 512 Hz
In first resonance, length = 30.7 cm
In second resonance length = 63.2 cm
(λ/2) = (63.2 – 30.7)cm
∴ (λ/2) = 32.5
∴ λ = 65 cm = 0.65 cm
velocity of sound = Vo = fλ = 332.8 m/s
∴ error observed = Vo – 330 = 332.8 – 330 = 2.8 m/s
∴ error = 2.8 m/s = 280 cm/s