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NEET2001PhysicsWaves and SoundActual

A source of frequency 240 ~Hz is moving towards an observer with a velocity of 20 ~m / s . The observer is now moving towards the source with a velocity of 20 ~m / s . Apparent frequency heard by observer, if velocity of sound is 340 ~m / s , is

Options

  1. A268 ~Hz
  2. B270 ~Hz
  3. C360 ~Hz
  4. D240 ~Hz .

Correct answer

B. 270 ~Hz

Step-by-step solution

Frequency of source n=240 ~Hz Velocity of source v_s=20 ~m / s Velocity of observer v₀=20 ~m / s Velocity of sound v=340 ~m / s Given both the source and the observer are moving towards each other. Hence the apparent frequency of the source is, aligned n^ & =n [ v+v₀ v-v_s ] & =240 [ 340+20 340-20 ] & =240 360 320 =270 ~Hz aligned

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