JEE Main 2020PhysicsWaves and SoundHardMCQ

JEE Main 2020Waves and Sound Question with Solution

JEE Main 2020 (04 Sep Shift 2)

Question

The driver of bus approaching a big wall notices that the frequency of his bus's horn changes from 420 Hz to 490 Hz when he hears it after it gets reflected from the wall. Find the speed of the bus if speed of the sound is 330 ms1:

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Show full solutionCorrect option: A
Correct answer
A91 kmh-1

Step-by-step explanation

Frequency appeared at wall

fw=330330-v.f    ......(1)

f'=330+v330·fw=330+v330-vf

490=330+v330-v·420

v=330×79125.38m/s=91Km/s

 

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About this question

This is a previous-year question from JEE Main 2020, covering the Waves and Sound chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.