A source which is situated at the centre of a circle is producing sound . Then the change in frequency (f) of sound heared by two persons at 'A' and 'B' if they move with velocities `20 m s^(-1)` and `10 m s^(-1)` , respectively , along the circular path as shown in figure is `"______"` . (Velocity of sound is `330 m s^(-1)`)

Options

A. 2f
B. f
C. zero
D. None of these

Answer

C

Explanation

As both the persons are moving at equal distance from the source along circular track, there is no change in frequency of sound heard by A and B .
`therefore` Change in frequency of sound = zero.