JEE Mains · Physics · STD 11 - 14. waves and sound
The frequency of echo will be \(.......Hz\) if the train blowing a whistle of frequency \(320\,Hz\) is moving with a velocity of \(36\,km / h\) towards a hill from which an echo is heard by the train driver. Velocity of sound in air is \(330\,m / s\).
- A \(320\)
- B \(340\)
- C \(360\)
- D \(380\)
Answer & Solution
Correct Answer
(B) \(340\)
Step-by-step Solution
Detailed explanation
The hill will be a secondary source. \(f _{1}=\) frequency of the car w.r.t. the hill \(f_{1}=\left(\frac{v}{v-v_{ s }}\right) f=\left(\frac{330}{320}\right) \times 320=330 Hz\) \(f _{2}=\) Frequency of the sound reflected by hill w.r.t. the car \((echo)\)…
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