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NEET
Exam
NEET
Subject
Physics
Chapter
Waves and Sound

NEET · Physics · Waves and Sound

A train whistling at constant frequency n is moving towards a...

A train whistling at constant frequency nn is moving towards a station at a constant speed vv. The train goes past a stationary observer on the station. The frequency nn of the sound as heard by the observer is plotted as a function of time tt. Identify the correct curve.A train whistling at constant frequency n is moving towards a station at a constant speed v . The train goes past aA train whistling at constant frequency n is moving towards a station at a constant speed v . The train goes past aA train whistling at constant frequency n is moving towards a station at a constant speed v . The train goes past aA train whistling at constant frequency n is moving towards a station at a constant speed v . The train goes past a

Options

  1. A∫_ π / 11 ^ 9 π / 22 d x 1+ x =
  2. B∫_ π / 11 ^ 9 π / 22 d x 1+ x =
  3. C∫_ π / 11 ^ 9 π / 22 d x 1+ x =
  4. D∫_ π / 11 ^ 9 π / 22 d x 1+ x =

Correct answer

D. ∫_ π / 11 ^ 9 π / 22 d x 1+ x =

Step-by-step solution

Since, the observer is stationary, so when train is approaching towards the observer or moving towards the observer, apparent frequency is given as, n′=nn^{\prime}=n\left(\frac{v}{v-v_{s}}\right)where,where,v_{s}isthespeedofsound.Itisclearfromtheaboveexpressionthatis the speed of sound. It is clear from the above expression thatn^{\prime}>n.However,whenthetrainisgoingawayfromtheobserver,thenapparentfrequency,. However, when the train is going away from the observer, then apparent frequency,n′=n(vv+vs)∴n′<n\begin{array}{ll} & n^{\prime}=n\left(\frac{v}{v+v_{s}}\right) \\ \therefore \quad & n^{\prime} < n \end{array}$Hence, graph represented in option (d) is correct.
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