A small source of sound moves on a circle as shown in figure (16-Q1) and an observer is sitting at O. Let v₁, v₂, v₃ be the frequencies heard when the source is at A, B and C respectively.

Question

A small source of sound moves on a circle as shown in figure (16-Q1) and an observer is sitting at O. Let v 1 , v 2 , v 3 be the frequencies heard when the source is at A, B and C respectively.

Philoid · Accepted Answer

When the source is at C the source speed is perpendicular to the line joining the observer and the source. Thus at this instant, the separation between the two is not changing and the frequency heard ν₃ is same as the source. When the source is at A the separation between them is increasing, so due to the Doppler effect ν₁ < ν₃. But when the source is at B, the separation is decreasing and due to the Doppler effect ν₃ < ν₂. So ν₂ > ν₃ > ν₁. Hence the option C is correct.

A small source of sound moves on a circle as shown in figure (16-Q1) and an observer is sitting at O. Let v1, v2, v3 be the frequencies heard when the source is at A, B and C respectively.

A small source of sound moves on a circle as shown in figure (16-Q1) and an observer is sitting at O. Let v₁, v₂, v₃ be the frequencies heard when the source is at A, B and C respectively.