A tuning fork of frequency 480 Hz is used in an experiment for measuring speed of sound (v) in air by resonance tube method. Resonance is observed to occur at two successive lengths of the air column, l1 = 30 cm and λ2 = 70 cm. Then, v is equal to -
(1) 338 ms–1 (2) 384 ms–1 (3) 379 ms–1 (4) 332 ms–1
