Waves - Result Question 76

78. A whistle of frequency 385Hz rotates in a horizontal circle of radius 50cm at an angular speed of 20 radians s1. The lowest frequency heard by a listener a long distance away at rest with respect to the centre of the circle, given velocity of sound equal to 340ms1, is [2002]

(a) 396Hz

(b) 363Hz

(c) 374Hz

(d) 385Hz

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Answer:

Correct Answer: 78. (c)

Solution:

  1. (c) Velocity of source, vs=rω

=0.50×20=10ms1

n=(vv+vs)n=340×385340+10=374Hz



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