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A car is moving towards a high cliff. The car driver sounds a horn of frequency ƒ. The reflected sound heard by the driver has frequency 2ƒ. If v be the velocity of sound, then the velocity of the car, in the same velocity units, will be
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- v/2
- v/√2
- v/3
- v/4
Correct Option: C
Let ƒ' be the frequency of sound heard by cliff.
| ∴ ƒ = | ..........(1) | |
| v - vc |
Now, for the reflected wave, cliff acts as a source,
| ∴ 2ƒ = | ..........(2) | |
| v |
| 2ƒ = | ||
| v - vc |
⇒ 2v - 2vc = v + vc or v/3 = vc
