A musician using and open flute of length 50 cm produces second harmonic sound waves. A person runs towards the musician from another end of a hall at a speed of 10 km/h. If the wave speed is 330 m/s, the frequency heard by the running person shall be close to :

Options

A. 333 Hz
B. 753 Hz
C. 666 Hz
D. 500 Hz

Answer

C

Explanation

Given, `lambda = (1)/(2)` m
Musician is a source of sound `upsilon_(s) = 0`
Actual frequency of sound, `f = (upsilon)/(lambda) = (330)/(1//2) = 660` Hz
Person approaches towards the sound
`upsilon_(0) = 10 km//h = (25)/(9) m//s`
Apparent frequency is heard by person
`f' = f ((upsilon + upsilon_(0))/(upsilon - upsilon_(s))) = 660 ((330 + (25)/(9))/(330))`
`= 665.55 ~~ 666` Hz