qies 42

Q.42 A source which is emitting sound of frequency f is initially at (– r, 0) and an observer is situated initially at (2r, 0). If observer and source both are moving with velocities $\overrightarrow{\mathrm{v}}$ _observer = – $\sqrt{2}\mathrm{V}\hat{\mathrm{i}}-\sqrt{2}\mathrm{V}\hat{\mathrm{j}}$ and $\overrightarrow{\mathrm{v}}$ _source = $\frac{\mathrm{V}}{\sqrt{2}}\hat{\mathrm{i}}+\frac{\mathrm{V}}{\sqrt{2}}\hat{\mathrm{j}}$ , then which of the following is correct option ?
  (A) Apparent frequency first increases, then decreases and observer observes the original frequency once during the motion. 
(B) Apparent frequency first increases, them decreases and observer ​ observes the original frequency twice ​during the motion. 

(C) ​Apparent frequency first increases, them decreases during the motion and obsercver never obseerves the initial frequency.
(D) Apparent frequency continuously decreases and once during the motion. observer hears the original frequency.