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MHT CET · Physics · Waves and Sound

Two sounding sources send waves at certain temperature in air of wavelength \(50 \mathrm{~cm}\) and \(50.5 \mathrm{~cm}\) respectively. The frequency of sources differ by \(6 \mathrm{~Hz}\). The velocity of sound in air at same temperature is

  1. A \(300 \mathrm{~m} / \mathrm{s}\)
  2. B \(303 \mathrm{~m} / \mathrm{s}\)
  3. C \(313 \mathrm{~m} / \mathrm{s}\)
  4. D \(330 \mathrm{~m} / \mathrm{s}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(303 \mathrm{~m} / \mathrm{s}\)

Step-by-step Solution

Detailed explanation

\(
\mathrm{v}=\mathrm{n} \lambda
\)
Since, both the sound sources are at same temperature, velocity of sound in both cases would be the same.
\(
\begin{aligned}
& \therefore \quad \mathrm{v}=\left(50 \mathrm{n}_{\mathrm{l}}\right) \mathrm{cm} / \mathrm{s} .....(i) \\
& \mathrm{v}=\left(50.5 \mathrm{n}_2\right) \mathrm{cm} / \mathrm{s} ....(ii)\\
& \frac{\mathrm{n}_1}{\mathrm{n}_2}=\frac{50.5}{50} ....[From (i) and (ii)]\\
& \therefore \quad \frac{\mathrm{n}_1-\mathrm{n}_2}{\mathrm{n}_2}=\frac{50.5-50}{50} \\
&
\end{aligned}
\)
\(\begin{array}{ll}\therefore & \frac{6}{\mathrm{n}_2}=\frac{0.50}{50}=\frac{1}{100} \quad \ldots .\left(\because \mathrm{n}_1-\mathrm{n}_2=6 \mathrm{~Hz}\right) \\ \therefore & \mathrm{n}_2=600 \mathrm{~Hz} \\ \therefore & \mathrm{v}=\frac{50.5 \times 600}{100} \mathrm{~m} / \mathrm{s} \ldots[\text { From (ii) }] \\ \therefore & \mathrm{v}=303 \mathrm{~m} / \mathrm{s}\end{array}\)