JEE Main 2015PhysicsWaves and SoundEasyMCQ

JEE Main 2015 — Waves and Sound Question with Solution

JEE Main 2015 (04 Apr)

Question

A train is moving on a straight track with speed 20 m s-1 . It is blowing its whistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as the train passes him is (speed of sound =320 m s-1 ) close to:

Choose an option

Show full solutionCorrect option: C
Correct answer
C12%

Step-by-step explanation

Before train passes

f′=vv-vs×f0

=320320-20×f0

=320300×f0

=16f015

After train passes

f′′=vv+vs×f0

f′′=320320+20f0

=320340f0

=1617f0

Change in frequency

=1615-1617f0

∴ Percentage change in frequency

=1615-1617f0f0×100 ≈12% nearly

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About this question

This is a previous-year question from JEE Main 2015, 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.