TS EAMCET · Physics · Waves and Sound
An observer is standing \(500 \mathrm{~m}\) away from a vertical hill. Starting between the observer and the hill, a police van sounding a siren of frequency \(1000 \mathrm{~Hz}\) moves towards the hill with a uniform speed. If the frequency of the sound heard directly from the siren is \(970 \mathrm{~Hz}\), the frequency of the sound heard after reflection from the hill (in Hz) is about, (velocity of sound \(=330 \mathrm{~ms}^{-1}\) ) :
- A 1042
- B 1032
- C 1022
- D 1012
Answer & Solution
Correct Answer
(B) 1032
Step-by-step Solution
Detailed explanation
Sound heard directly \(f_1=f_o\left(\frac{v}{v+v_s}\right)\) \(\therefore \quad 970=1000\left(\frac{330}{330+v_s}\right)\) or \(\quad v_s=10.2 \mathrm{~m} / \mathrm{s}\) The frequency of reflected sound is given by \(f_2=f_o\left(\frac{v}{v-v_s}\right)\)…
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