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A source is moving towards an observer with a speed of 20 m / s and having frequency of 240 Hz . The observer is now moving towards the source with a speed of 20 m / s . Apparent frequency heard by observer, if velocity of sound is 340 m / s , is

A

240 Hz

B

270 Hz

C

360 Hz

D

268 Hz

Text Solution

Verified by Experts

The correct Answer is:
B
In this case, both the source and the observer, are moving towards each other, then the apparent frequency
`n' = ((v + v_(o))/(v- v_(s)))n`
`= ((340 + 20)/(340 - 20)) xx 240`
`= (360)/(320) xx 240 = 2440 xx (9)/(8) = 270 Hz`
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