Q149 / 160 · AP EAMCET 2020 (18 Sep Shift 2) · Physics
A sound source is moving towards a stationary listener with \(1 / 10\) th of the speed of sound. The ratio of apparent to real frequency is
- Correct answerA\(\frac{10}{9}\)
- B\(\frac{11}{10}\)
- C\(\left(\frac{11}{10}\right)^2\)
- D\(\left(\frac{9}{10}\right)^2\)
Solution
Speed of sound source towards stationary observer
\(v_s=\frac{v}{10}\)
where, \(v\) is the speed of sound.
\(\therefore\) Apparent frequency, \(f^{\prime}=\left(\frac{v}{v-v_s}\right) f\)
\(\begin{aligned}
& =\left(\frac{v}{v-\frac{v}{10}}\right) f \\
\Rightarrow f^{\prime} & =\frac{10}{9} f \Rightarrow \frac{f^{\prime}}{f}=\frac{10}{9}
\end{aligned}\)
Hence, the correct answer is option: 'A'.