A train moving at a speed of 220 ms-1 towards a stationary object, emits a sound of frequency 1000 Hz. Some of the sound reaching the object gets reflected back to the train as an echo. The frequency of the echo as detected by the driver of the train is
(speed of sound in air is 330 ms-1)
1. 3500Hz
2. 4000Hz
3. 5000Hz
4. 3000Hz

Subtopic:  Doppler's Effect (OLD NCERT) |
 65%
From NCERT
NEET - 2012
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Two waves are represented by the equations y1=a sin (ωt+kx+0.57)m and y2=a cos (ωt+kx)m, where x is in metre and t in second. The phase difference between them is?

(1) 1.25 rad

(2) 1.57 rad

(3) 0.57 rad

(4) 1.0 rad

Subtopic:  Wave Motion |
 61%
From NCERT
NEET - 2011
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Sound waves travel at 350 m/s through a warm 

air and at 3500 m/s through brass. The wavelength

of a 700 Hz acoustic wave as it enters brass from 

warm air :

(1) increases by factor 20

(2) increases by factor 10

(3) decreases by factor 20

(4) decreases by factor 10

Subtopic:  Wave Motion |
 76%
From NCERT
NEET - 2011
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Two identical piano wires kept under the same tension T have a fundamental frequency of 600 Hz. The fractional increase in the tension of one of the wires which will lead to the occurrence of 6 beats/s when both the wires oscillate together would be:

1. 0.02 2. 0.03
3. 0.04  4. 0.01
Subtopic:  Beats |
 54%
From NCERT
NEET - 2011
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Two particles are oscillating along two close parallel straight lines side by side, with the same frequency and amplitudes. They pass each other, moving in opposite directions when their displacement is half of the amplitude. The mean positions of the two particles lie on a straight line perpendicular to the paths of the two particles. The phase difference is :

(1)zero                                 

(2)2π3

(3)π                                     

(4)π6

Subtopic:  Wave Motion |
 55%
From NCERT
NEET - 2011
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A transverse wave is represented by y=A sin ωt-kx. For what value of the wavelength is the wave velocity equal to the maximum particle velocity?

(1) π A/2                                           

(2) π A

(3) 2 π A                                           

(4) A

Subtopic:  Types of Waves |
 83%
From NCERT
NEET - 2010
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A tuning fork of frequency 512 Hz makes 4 beats/s with the vibrating strings of a piano. The beat frequency decreases to 2 beats/s when the tension in the piano strings is slightly increased. The frequency of the piano string before increasing the tension was:
1. 510 Hz                       
2. 514 Hz
3. 516 Hz                       
4. 508 Hz

Subtopic:  Beats |
 70%
From NCERT
NEET - 2010
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A wave in a string has an amplitude of 2 cm. The wave travels in the +ve direction of x-axis with a speed of 128 ms-1 and it is noted that 5 complete waves fit in 4 m length of the string. The equation describing the wave is :

(1) y=0.02m sin 7.85x +1005 t 

(2) y=0.02m sin 15.7x -2010 t 

(3) y=0.02m sin 15.7x +2010 t 

(4) y=0.02m sin 7.85x -1005 t 

Subtopic:  Travelling Wave on String |
 67%
From NCERT
NEET - 2009
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Each of the two strings of length 51.6 cm and 49.1 cm are tensioned separately by 20N force. Mass per unit length of both the strings is same and equal to 1 gm-1When both the strings vibrate simultaneously the number of beats is :

1. 5                                                   

2. 7

3. 8                                                   

4. 3

Subtopic:  Beats |
 59%
From NCERT
NEET - 2009
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Two periodic waves of intensities  I1 and I2 pass through a region at the same time in the same direction. The sum of the maximum and  minimum intensities is :

(1) I1+I2

(2) I1+I22

(3)I1-I22

(4) 2 I1+I2 

 

Subtopic:  Wave Motion |
 70%
From NCERT
NEET - 2008
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