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JEE Main202225 Jul 2022Morning ShiftPhysicsWaves and SoundActual

An observer is riding on a bicycle and moving towards a hill at 18 km h - 1 . He hears a sound from a source at some distance behind him directly as well as after its reflection from the hill. If the original frequency of the sound as emitted by source is 640 Hz and velocity of the sound in air is 320 m s - 1 , the beat frequency between the two sounds heard by observer will be _____ Hz .

Correct answer

0

Step-by-step solution

Here, V S = 0 , V ob = 18 5 18 = 5   m   s - 1 Frequency, f direct   = 320 - 5 320 640 = 630   Hz f reflected   = 320 + 5 320 640 = 650   Hz Thus, beat frequency, f beat   = 650 - 630 = 20   Hz

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