A source of sound is traveling towards a stationary observer. The frequency of the sound heard by the observer is three times the original frequency. The velocity of sound is v m/sec. The speed of the source will be :

(1) 23v

(2) v

(3) 32v

(4) 3v

Subtopic:  Doppler's Effect (OLD NCERT) |
 82%
From NCERT
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A sound source is moving towards a stationary observer with 1/10 of the speed of sound. The ratio of apparent to real frequency is : 

(1) 10/9

(2) 11/10

(3) (11/10)2

(4) (9/10)2

Subtopic:  Doppler's Effect (OLD NCERT) |
 85%
From NCERT
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The speed of sound in air at a given temperature is 350 m/s. An engine blows whistle at a frequency of 1200 cps. It is approaching the observer with velocity 50 m/s. The apparent frequency in cps heard by the observer will be :

(1) 600

(2) 1050

(3) 1400

(4) 2400

Subtopic:  Doppler's Effect (OLD NCERT) |
 86%
From NCERT
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The Doppler's effect is applicable for :

(1) Light waves

(2) Sound waves

(3) Space waves

(4) Both (1) and (2)

Subtopic:  Doppler's Effect (OLD NCERT) |
 70%
From NCERT
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A source of sound is moving with constant velocity of 20 m/s emitting a note of frequency 1000 Hz. The ratio of frequencies observed by a stationary observer while the source is approaching him and after it crosses him will be

(1) 9 : 8

(2) 8 : 9

(3) 1 : 1

(4) 9 : 10

(Speed of sound v = 340 m/s)

Subtopic:  Doppler's Effect (OLD NCERT) |
 76%
From NCERT
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A source and listener are both moving towards each other at a speed of v/10, where v is the speed of sound. If the frequency of the note emitted by the source is f, the frequency heard by the listener would be nearly :
1. 1.11 f
2. 1.22 f
3. f
4. 1.27 f

Subtopic:  Doppler's Effect (OLD NCERT) |
 80%
From NCERT
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A motor car blowing a horn of frequency 124vib/sec moves with a velocity 72 km/hr towards a tall wall. The frequency of the reflected sound heard by the driver will be (velocity of sound in air is 330 m/s) 

(1) 109 vib/sec

(2) 132 vib/sec

(3) 140 vib/sec

(4) 248 vib/sec

Subtopic:  Doppler's Effect (OLD NCERT) |
 65%
From NCERT
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A source of sound of frequency n is moving towards a stationary observer with a speed S. If the speed of sound in air is V and the frequency heard by the observer is n1, the value of n1/n is 

(1) (V + S)/V

(2) V/(V + S)

(3) (VS)/V

(4) V/(VS)

Subtopic:  Doppler's Effect (OLD NCERT) |
 79%
From NCERT
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An observer is moving away from the source of the sound of frequency 100 Hz. His speed is 33 m/s. If the speed of sound is 330 m/s, then the observed frequency is :

(1) 90 Hz

(2) 100 Hz

(3) 91 Hz

(4) 110 Hz

Subtopic:  Doppler's Effect (OLD NCERT) |
 72%
From NCERT
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An observer standing at the station observes frequency 219 Hz when a train approaches and 184 Hz when train goes away from him. If velocity of sound in air is 340 m/s, then velocity of train and actual frequency of whistle will be 

(1) 15.5ms1,200Hz

(2) 19.5ms1,205Hz

(3) 29.5ms1,200Hz

(4) 32.5ms1,205Hz

Subtopic:  Doppler's Effect (OLD NCERT) |
 67%
From NCERT
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