Question

A curve is plotted to represent the dependence of the ratio of the received frequency $f$ to the frequency $f_0$ emitted by the source on the ratio of the speed of observer $V_{\text{ob}}$ to the speed of sound $V_{\text{sound}}$ in a situation in which an observer is moving towards a stationary sound source. The curve is best represented by:

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

Given,
received frequency by observer $=f$,
emitted frequency by the source $=f_0$,
As the source is stationary, so $V_{\text{source}}=0$

From doppler’s effect when observer comes near to sound source, the apparent frequency observed by observer
$f=f_0(1+\frac{V_{\text{ob}}}{V_{\text{sound}}})$

$\frac{f}{f_0}=(1+\frac{V_{\text{ob}}}{V_{\text{sound}}})\dots \left(i\right)$

When $\frac{V_{\text{ob}}}{V_{\text{sound}}}=0$, $\Rightarrow \frac{f}{f_0}=1$

When $\frac{V_{\text{ob}}}{V_{\text{sound}}}=1$, $\Rightarrow \frac{f}{f_0}=2$

By the obtained values we can draw the curve i.e.

Final Answer: (a)