# DOPPLER'S EFFECT ---IIT JEE,AIEEE,AIPMT Online Test

the listener is moving towards the source

the source is moving towards the listener

the listener is moving away from the source

the listener has a defective ear

A source and an observer are moving towards each other with a speed equal to where be the speed of sound. The source is emitting sound of frequency n. The frequency heard by the observer is ____.

Zero

/

540 m/s

270 m/s

85 m/s

52.5 m/s

A police car horn emits a sound at a frequency 240 Hz when the car is at rest. If the speed of the sound is 330 m/s, the frequency heard by an observer who is approaching the car at a speed of 11 m/s, is ____.

248 Hz

244 Hz

240 Hz

230 Hz

A bus is moving with a velocity of 5 m/s towards a huge wall. The driver sounds a horn of frequency 165 Hz. If the speed of sound in air is 355 m/s, the number of beats heard per second by a passenger on the bus is ____.

6

5

3

4

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

240 Hz

270 Hz

280 Hz

360 Hz

A whistle revolves in a circle with an angular speed of 20 rad/sec using a string of length 50 cm. If the frequency of sound from the whistle is 385 Hz, then what is the minimum frequency heard by an observer, which is far away from the centre in the same plane? (v = 340 m/s) ____.

333 Hz

374 Hz

385 Hz

394 Hz

A Siren emitting sound of frequency 800 Hz is going away from a static listener with a speed of 30 m/s, frequency of the sound to be heard by the listener is (take velocity of sound as 330 m/s) ____.

733.3 Hz

644.8 Hz

481.2 Hz

286.5 Hz

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