$4$

$1242644$

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 robserver $=-\sqrt[\phantom{2}]{2}$hat$(Vi)-\sqrt[\phantom{2}]{2}$Vhat$(j)$ and vec$(v{)}_{\text{s}\text{o}\text{u}\text{r}\text{c}\text{e}}=\frac{V}{\sqrt[\phantom{2}]{2}}$hat$(i)+\frac{V}{\sqrt[\phantom{2}]{2}}$hat$(j),$ then which of the following is correct option?

$1$ Apparent frequency first increases, then decreases and observer observes the original frequency once during the motion.

$3998\%$ Marked this option

$2$ Apparent frequency first increases, then decreases and observer observes the original frequency twice during the motion.

$35\mathrm{.}5\%$ Marked this option

$3$ Apparent frequency first increases, then decreases during the motion and observer never observes the initial frequency.

$21\mathrm{.}52\%$ Marked this option

$4$ Apparent frequency continuously decreases and once during the motion, observer hears the original frequency. $15\mathrm{.}99\%$ Marked this option

$15\mathrm{.}99\%$ of students got it right