TS EAMCET · Physics · Waves and Sound
A highway truck has two horns \(A\) and \(B\). When sounded together, the driver records 50 beats in 10 seconds. With horn \(B\) blowing and the truck moving towards a wall at a speed of \(10 \mathrm{~m} / \mathrm{s}\), the driver noticed a beat frequency of \(5 \mathrm{~Hz}\) with the echo. When frequency of \(A\) is decreased the beat frequency with two horns sounded together increases. Calculate the frequency of horn \(A\). (Speed of sound in air \(=330 \mathrm{~m} / \mathrm{s}\) )
- A \(75 \mathrm{~Hz}\)
- B \(85 \mathrm{~Hz}\)
- C \(90 \mathrm{~Hz}\)
- D \(95 \mathrm{~Hz}\)
Answer & Solution
Correct Answer
(A) \(75 \mathrm{~Hz}\)
Step-by-step Solution
Detailed explanation
Here, Iet frequencies of hom \(A\) and \(B\) are \(n_A\) and \(n_B\), respectively. As given, \[ \begin{aligned} & n_A-n_B=\frac{50}{10} \\ & n_A-n_B=5 \text { beats } \end{aligned} \] When, the hom \(B\) is blown while moving towards the wall the apparent frequency,…
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