JEE Main · 2005 · 08 May 2005 · Offline · Waves & Sound

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An observer moves towards a stationary source of sound, with a velocity one fifth of the velocity of sound. What is the percentage increase in the apparent frequency?

(A)zero.
(B) $0.5%$
(C) $5%$
(D) $20%$ ✓ Correct

Answer: (D)

Solution

For an observer moving towards a stationary source,

f^{'} = \frac{v + v _{o}}{v} f_{0}

. With

v_{o} = \frac{v}{5}

f^{'} = \frac{v + v /5}{v} f_{0} = \frac{6}{5} f_{0}

, an increase of

\frac{f ^{'} - f _{0}}{f _{0}} = \frac{1}{5} = 20%

JEE Main · 2005 · 08 May 2005 · Offline · Single correct option

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