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A motor cyclist moving with 30 km/ h blo...

A motor cyclist moving with 30 km/ h blows a whistle of 476 Hz towards a cliff. If velocity of sound is 1220 Km/h, the apparent frequency of the echo heard by him is :

A

250 Hz

B

500 Hz

C

425 Hz

D

476 Hz.

Text Solution

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The correct Answer is:
B
When the ,motor cyclist is approaching stationary wall i. e. observer then
`v. = ((1220)/(1220 - 30)) 476 = 488 Hz.`
` therefore` Frequency of reflected wave i.e., echo is 488 Hz and observer is moving towards it.
`therefore v.. = ((1220 + 30)/(1220)) 488` = 500 Hz.
hence the correct choice is (b) .
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