Question

A tuning fork of frequency n is sounded at the open end of a long cylindrical tube having a side opening and fitted with a movable reflecting piston. On moving the piston through 9 cm, the intensity of sound heard by the listener changes from maximum to minimum. If speed of sound is 360 m/s, value of n is –

• A. 1000 Hz
• B. 250 Hz
• C. 500 Hz
• D. 750 Hz

Answer 1

Answer: (A)

1000 Hz

Answer 2

maximum to minimum $\frac { \lambda } { 2 }$= a + a = 18 cm

Q n = $\frac { v } { \lambda }$ \ l = 36 cm