Question

A source of sound stationary with respect to medium emits sound of frequency $f$ and wavelength $\lambda$. The speed of sound with respect to medium is $C$, speed of medium is $V_m$. The observer $O_1$ receives waves of frequency $f_1$ and wavelength ${\lambda }_1$. The observer $O_2$ receives waves of frequency $f_2$ and wavelength ${\lambda }_2$.Match the column given below if $V_s$ is speed of source with respect to ground.

Answer 1

In case A as the source is not moving and only observers are moving the effect will be only on frequency and wavelength remain the same.Frequency of sound heard by observer 2 will increase as its moving closer to source hence meeting more sound waves.

Case B source is moving closer to observer 1 hence the wavelength will decrease and frequency will increase.

Case C as the medium is moving forward the effect will be opposite of case B but can't comment on frequency as it depends on velocities of observer and source.

Case D similar to case B but only the relative velocity is less .