A listener is at rest with respect to the souce of sound. A wind starts blowing along the line joining the source and the observer. Which of the following quantities do not change?

A listener is at rest with respect to the souce of sound. A wind start

1.	A listener is at rest with respect to the souce of sound. A wind starts blowing along the line joining the source and the observer. Which of the following quantities do not change?
Answer» Frequency Velocity of sound wavelength time period Answer :A::D