A boy is walking away from a wall towards an observer at a speed of 1 metre/sec and blows a whistle whose frequency is 680 Hz. The number of beats heard by the observer per second is (Velocity of sound in air = 340 metres/sec 

(1) Zero

(2) 2

(3) 8

(4) 4

Concept Questions :-

Doppler effect
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The driver of a car travelling with speed 30 metres per second towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 metres per second, the frequency of the reflected sound as heard by the driver is :

(1) 720 Hz

(2) 555.5 Hz

(3) 550 Hz

(4) 500 Hz

Concept Questions :-

Doppler effect
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A source of sound is travelling with a velocity 40 km/hour towards the observer and emits the sound of frequency 2000 Hz. If the velocity of sound is 1220 km/hour, then what is the apparent frequency heard by an observer 

(1) 2210 Hz

(2) 1920 Hz

(3) 2068 Hz

(4) 2086 Hz

Concept Questions :-

Doppler effect
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A source of sound and listener are approaching each other with a speed of 40 m/s. The apparent frequency of note produced by the source is 400 cps. Then, its true frequency (in cps) is (velocity of sound in air = 360 m/s

(1) 420

(2) 360

(3) 400

(4) 320

Concept Questions :-

Doppler effect
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A siren emitting sound of frequency 500 Hz is going away from a static listener with a speed of 50 m/sec. The frequency of sound to be heard, directly from the siren, is :

(1) 434.2 Hz

(2) 589.3 Hz

(3) 481.2 Hz

(4) 286.5 Hz

Concept Questions :-

Doppler effect
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A man sitting in a moving train hears the whistle of the engine. The frequency of the whistle is 600 Hz 

(1) The apparent frequency as heard by him is smaller than 600 Hz

(2) The apparent frequency is larger than 600 Hz

(3) The frequency as heard by him is 600 Hz

(4) None of the above

Concept Questions :-

Doppler effect
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A whistle of frequency 500 Hz tied to the end of a string of length 1.2 m revolves at 400 rev/min. A listener standing some distance away in the plane of rotation of whistle hears frequencies in the range (speed of sound = 340 m/s

(1) 436 to 586

(2) 426 to 574

(3) 426 to 584

(4) 436 to 674

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A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is f1. If the train’s speed is reduced to 17 m/s, the frequency registered is f2. If the speed of sound is 340 m/s then the ratio f1/f2 is 

(1) 18/19

(2) 1/2

(3) 2

(4) 19/18

Concept Questions :-

Doppler effect
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If source and observer both are relatively at rest and if speed of sound is increased then frequency heard by observer will :

(1) Increases

(2) Decreases

(3) Can not be predicted

(4) Will not change

Concept Questions :-

Doppler effect
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A source and an observer move away from each other with a velocity of 10 m/s with respect to ground. If the observer finds the frequency of sound coming from the source as 1950 Hz, then actual frequency of the source is (velocity of sound in air = 340 m/s) 

(1) 1950 Hz

(2) 2068 Hz

(3) 2132 Hz

(4) 2486 Hz

Concept Questions :-

Doppler effect
To view Explanation, Please buy any of the course from below.
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level: