Waves - Result Question 75

77. An observer moves towards a stationary source of sound with a speed 1/5 th of the speed of sound. The wavelength and frequency of the sound emitted are λ and f respectively. The apparent frequency and wavelength recorded by the observer are respectively.

[2003]

(a) 0.8f,0.8λ

(b) 1.2f,1.2λ

(c) 1.2f,λ

(d) f,1.2λ

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Answer:

Correct Answer: 77. (c)

Solution:

  1. (c) Wavelength remains constant (unchanged) in this case.

fapparent =(u+u/5u)f=65f=1.2f



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