Question

A whistle emitting a loud sound of frequency 540 Hz is whirled in a horizontal circle of radius 2 m and at a constant angular speed of 15 rad/s. The speed of sound is 330 m/s. The ratio of the highest to the lowest frequency heard by a listener standing at rest at a large distance from the center of the circle is

(A)  1.0

(B)  1.1

(C)  1.2

(D)  1.4 

Answer 1

Correct option (C) 1.2

Explanation:

v₁ and v₂ are speed of whistle

| v₁ | = | v₂ | = ωr 

 = 15 x 2 = 30 m/s

Maximum frequency heard → 

Here,

f → original frequency (540 Hz)

v → speed of sound 

 v_s→speed of whistle