There is a source of sound (a tuning fork) moving towards a reflecting wall will a speed of 30 m s - 1 . The velocity of the sound in air is 330 m s - 1 and the frequency of the tuning fork is 600 Hz

Question

There is a source of sound (a tuning fork) moving towards a reflecting wall will a speed of $30 m s^{- 1}$ . The velocity of the sound in air is $330 m s^{- 1}$ and the frequency of the tuning fork is $600 Hz$ . The observer is between the source and the wall and is moving with some velocity $V_{1}$ towards the wall. The beat frequency heard by the observer is $4 Hz$ . If the tuning fork is waxed, the frequency beats heard by the observer becomes $3 Hz$ . If the new frequency of tuning fork is $k$ then $\frac{k}{50}$ is

TestHub · Accepted Answer

Apparent frequency of source = n 0 c - v 1 c - v 2 = n ′ Apparent frequency of reflected sound = n 0 c + v 1 C - V = n ′ ′ Beat frequency = n ′ ′ - n ′ = 2 n 0 V 1 C - V 2 = 2 × 600 × V 1 330 - 30 = 4 Hz ∴ V 1 = 1 m s - 1 When the tuning fork is waxed let its frequency become k Beat frequency = 2 k v 1 C - V 2 = 2 × k × 1 330 × 30 = 3 H z ∴ k = 450 H z = new frequency of tuning fork. k 50 = 9

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