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The driver of a car travelling with speed 30 m/sec towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 m/s, the frequency of reflected sound as heard by driver is
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- 555.5 Hz
- 720 Hz
- 500 Hz
- 550 Hz
Correct Option: B
f ′ is the apparent frequency received by an observer at the hill. f ′′ is the frequency of the reflected sound as heard by driver.
| f' = | f, | |
| v - 30 |
| f" = | f, | f = | × 600 | |||
| v | v - 30 | 300 |
= 720 Hz
