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

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Important Questions on Doppler Effect

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11th ICSE
IMPORTANT
ISC Physics Class XI Part 1>Chapter 33 - Doppler Effect>FOR DIFFERENT COMPETITIVE EXAMINATIONS>Q 8
An observer moves towards a stationary source of sound, with a velocity one-fifth of the velocity of sound. What is the percentage increase in the apparent frequency ?
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11th ICSE
IMPORTANT
ISC Physics Class XI Part 1>Chapter 33 - Doppler Effect>FOR DIFFERENT COMPETITIVE EXAMINATIONS>Q 9

A sound-source produces waves of length 60 cm. This source is moving towards a stationary observer with a speed 15th the speed of sound. The wavelength as judged by the observer is :

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11th ICSE
IMPORTANT
ISC Physics Class XI Part 1>Chapter 33 - Doppler Effect>FOR DIFFERENT COMPETITIVE EXAMINATIONS>Q 10
A speeding motorcyclist sees traffic jam ahead of him. He slows down to 36 km h-1. He finds that traffic has eased and a car moving ahead of him at  18 km h-1 is honking at a frequency of 1392 Hz. If the speed of sound is 343 m s-1, the frequency of the honk as heard by him will be :
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11th ICSE
IMPORTANT
ISC Physics Class XI Part 1>Chapter 33 - Doppler Effect>FOR DIFFERENT COMPETITIVE EXAMINATIONS>Q 11
A  sound-source whose real frequency is 500 hertz, is moving on a circular path. A person standing at the centre of the circle will hear a frequency of:
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11th ICSE
IMPORTANT
ISC Physics Class XI Part 1>Chapter 33 - Doppler Effect>FOR DIFFERENT COMPETITIVE EXAMINATIONS>Q 12
A whistle is whirled in a circle of radius 1.0 m, completing the circular path twice per second. The velocity of sound is 332 ms-1. A person is standing outside the circle but in the plane of the circle. The ratio of the highest and the lowest frequency of the sound heard by him:
MEDIUM
11th ICSE
IMPORTANT
ISC Physics Class XI Part 1>Chapter 33 - Doppler Effect>FOR DIFFERENT COMPETITIVE EXAMINATIONS>Q 13
A person is observing two trains, one is coming towards him with a velocity of 4 m s-1 and, the other is going away from him with the same velocity. If the trains sound with their natural frequency 240 Hz, then what will be the beat frequency heard by the person? Speed of sound is 320 m s-1.
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11th ICSE
IMPORTANT
ISC Physics Class XI Part 1>Chapter 33 - Doppler Effect>FOR DIFFERENT COMPETITIVE EXAMINATIONS>Q 14
A siren placed on a railway platform emits sound of frequency 5 kHz. A passenger sitting in a train A moving towards the siren records the frequency of the siren as 5.5 kHz. Now, the passenger sitting in another train B, which is returning towards the siren, records the frequency of the siren as 6.0 kHz. Then, the ratio of the speeds of the trains B and is A:
MEDIUM
11th ICSE
IMPORTANT
ISC Physics Class XI Part 1>Chapter 33 - Doppler Effect>FOR DIFFERENT COMPETITIVE EXAMINATIONS>Q 15
A motorcycle starts from rest and accelerates along a straight path at 2 m/s2. At the starting point of the motorcycle there is a stationary electric siren. How far has the motorcycle gone when the driver hears the frequency of the siren at 94% of its value when the motorcycle was at rest ? (speed of sound = 330 ms-1)