A police car with a siren of frequency 8 kHz is moving with uniform velocity 36 km h - 1 towards a tall building which reflects the sound waves. The speed of sound in air is 320 m s - 1 . The frequency of the siren heard by the car driver is

Question

A police car with a siren of frequency 8 kHz is moving with uniform velocity 36 km h - 1 towards a tall building which reflects the sound waves. The speed of sound in air is 320 m s - 1 . The frequency of the siren heard by the car driver is, 8 . 5 kHz, 8 . 25 kHz, 7 . 25 kHz, 7 . 5 kHz

MARKS App · Accepted Answer

36 km h - 1 = 36 × 5 18 = 10 m s - 1 Apparent frequency of sound heard by car driver (observer) f ′′ = f v + v o v - v s = 8 320 + 10 320 - 10 f ′′ = 8 .5 kHz

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