JEE Main201910 Apr 2019Evening ShiftPhysicsWaves and SoundActual
A source of sound S is moving with a velocity of 50 m s - 1 towards a stationary observer. The observer measures the frequency of the source as 1000 H z . What will be the apparent frequency of the source when it is moving away from the observer after crossing him? (Take velocity of sound in air is 350 m s - 1 )
Options
- A750 H z
- B857 H z
- C1143 H z
- D807 H z
Correct answer
A. 750 H z
Step-by-step solution
When source approaches, f 1 = f 0 v v - v s When source recedes, f 2 = f 0 v v + v s ⇒   f 2 f 1 = v - v s v + v s ⇒ f 2 = 1000 × 350 - 50 350 + 50   H z = 750   H z