MHT CET · Physics · Waves and Sound
A source of sound is moving towards a stationary observer with \(\left(\frac{1}{10}\right)^{\text {th }}\) the of the speed of sound. The ratio of apparent to real frequency is
- A \(10:9\)
- B \(11:10\)
- C \((11)^2:(10)^2\)
- D \((9)^2:(10)^2\)
Answer & Solution
Correct Answer
(A) \(10:9\)
Step-by-step Solution
Detailed explanation
For source of sound moving towards a stationary observer, the apparent frequency is given by, \(\mathrm{n}=\mathrm{n}_0 \times \frac{\mathrm{v}}{\mathrm{v}-\mathrm{v}_{\mathrm{S}}}\)
\(\begin{aligned}
& \therefore \quad \frac{\mathrm{n}}{\mathrm{n}_0}=\frac{\mathrm{v}}{\mathrm{v}-\frac{\mathrm{v}}{10}} \\
& \therefore \quad \frac{\mathrm{n}}{\mathrm{n}_0}=\frac{10}{9}
\end{aligned}\)
\(\begin{aligned}
& \therefore \quad \frac{\mathrm{n}}{\mathrm{n}_0}=\frac{\mathrm{v}}{\mathrm{v}-\frac{\mathrm{v}}{10}} \\
& \therefore \quad \frac{\mathrm{n}}{\mathrm{n}_0}=\frac{10}{9}
\end{aligned}\)
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