Q52 / 75 · JEE Main 2020 (06 Sep Shift 1) · Physics

A sound source S is moving along a straight track with speed v, and is emitting sound of frequency v0.An observer is standing at a finite distance, at the point O, from the track. The time variation of frequency heard by observer is best represented by : (to represents the instant when the distance between the source and observer is minimum)

  • A
    Figure
  • Correct answer
    B
    Figure
  • C
    Figure
  • D
    Figure

Solution

Figure  

Observed frequency will be v=Vsound +VcosθVsound v0

Using this formula we can say that observed frequency will decrease continuously and it becomes equal to original frequency when θ= 90°. So correct graph is

Figure 

 

Hence, the correct answer is option: 'B'.

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