**NEET Physics Chapter Wise Mock Test – Waves**

**Question 1:
**The sound waves are reflected from an obstacle into the same medium for which they were incident. Which of the following changes?

(a) Speed

(b) Frequency

(c) Wavelength

(d) None of these

**Question 2:
**The waves produced by a motorboat sailing in water are

(a) transverse

(b) longitudinal

(c) longitudinal and transverse

(d) stationary

**Question 3:
**A wave of frequency 500 Hz travels between X and Y, distance’ of 600 m in 2 s. How many wavelength are there in distance XY?

(a) 1000

(b) 300

(c) 180

(d) 2000

**Question 4:
**A boat at anchor is rocked by waves whose crests are 100 m apart and velocity is 25 ms

^{-1}. The boat bounces up once in every

(a) 2500 s

(b) 75 s

(c) 4 s

(d) 0.25 s

**Question 5:
**Sound waves of wavelength λ travelling in a medium with a speed of v m/s enter into another medium where its speed is 2v m/s. Wavelength of sound waves in the second medium is

(a) λ

(b) λ/2

(c) 2λ

(d) 4λ

**Question 6:
**An observer standing on the sea coast finds that 54 ripples reach the surface per minute. If the wavelength of the ripples be 10 m, what is the wave velocity?

(a) 54 m/s

(b) 9m/s

(c) 10 m/s

(d) 6m/s

**Question 7:
**A wave is represented by the equation

y = 7 sin(7πt-0.04x+π/3)

where, x in metre and t in second. The speed of the wave is

(a) 175π ms

^{-1}

(b) 49π ms

^{-1}

(c) 49/π ms

^{-1}

(d) 0.28π ms

^{-1}

**Question 8:
**In the given progressive wave equation,

y =0.5 sin(10πt-2x) cm

What is the maximum velocity of particle?

(a) 5 ms

^{-1}

(b) 5 pi ms

^{-1}

(c) 10 ms

^{-1}

(d) 10.5 ms

^{-1}

**Question 9:
**A transverse wave propagating along X-axis is represented by

y(x,t) = 8.0 sin(0.5πx-4πt-π/4)

where, x is in metre and t is in second. The speed of the wave is

(a) 4π ms

^{-1}

(b) 0.5π ms

^{-1}

(c) π/4 ms

^{-1}

(d) 8 ms

^{-1}

**Question 10:
**Velocity of sound in a gaseous medium is 330 ms

^{-1}. If the pressure is increased by 4 times without change in temperature, the velocity of sound in the gas is

(a) 330 ms

^{-1}

(b) 660 ms

^{-1}

(c) 156 ms

^{-1}

(d) 990 ms

^{-1}

**Question 11:
**The displacement Y of a particle in a medium can be expressed as

y = 10

^{-6}sin (100t+ 20x + π/4) m where, t is in second and x in metre.

The speed of the wave is

(a) 2000 ms

^{-1}

(b) 5 ms

^{-1}

(c) 20ms

^{-1}

(d) 5π ms

^{-1}

**Question 12:
**The phase difference between two waves, represented by

**where, x is expressed in metre and t is expressed in second, is approximately**

(a) 1.07 rad

(b) 2.07 rad

(c) 0.5 rad

(d) 1.5 rad

**Question 13:
**

**Question 14:
**

**Question 15:
**

**Question 16:
**Ratio of amplitude of two interfering waves is 2:1, then ratio of amplitude of maxima to minima is

(a) 4 :1

(b) 9:1

(c) 3 :1

(d) 9:4

**Question 17:
**If two waves of amplitude a produce a resultant wave of amplitude a, then the phase difference between them will be

(a) 60°

(b) 90°

(c) 120°

(d) 180°

**Question 18:
**The equation of a stationary wave is y = 0.8 cos(π x/20)sin 200πt

where x is in cm. and t is in second. The separation between consecutive nodes will be

(a) 20 cm

(b) 10cm

(c) 40 cm

(d) 30 cm

**Question 19:
**Standing waves are produced in 10 m long stretched string. If the string vibrates in five segments and wave velocity is 20 ms

^{-1}, then its frequency will be

(a) 5 Hz

(b) 2 Hz

(c) 10 Hz

(d) 15 Hz

**Question 20:
**An organ pipe, open from both ends produced 5 beats/s when vibrated with a source of frequency 200 Hz in its fundamental mode. The second harmonic of the same pipe produces 10 beats/s with a source of frequency 420 Hz. The fundamental frequency of pipe is

(a) 195 Hz

(b) 205 Hz

(c) 190 Hz

(d) 210 Hz

**Question 21:
**The fundamental frequency of a closed pipe is 220 Hz. If 1/4 of the pipe is filled with water, the frequency of the 1st overtone of the pipe now is

(a) 220 Hz

(b) 440 Hz

(c) 880 Hz

(d) 1760 Hz

**Question 22:
**In a resonance pipe the 1st and 2nd resonances are obtained at depths 22.7 cm and 70.2 cm, respectively. What will be the end correction?

(a) 1.05 cm

(b) 1115.5 cm

(c) 92.5 cm

(d) 113.5 cm

**Question 23:
**An organ pipe closed at one end has fundamental frequency of 1500 Hz. The maximum number of overtones generated by this pipe which a ftormal person can hear is?

(a) 4

(b) 13

(c) 6

(d) 9

**Question 24:
**The length of a sonometer wire AB is 110 cm. Where should the two bridges be placed from A to divide the wire in three segments whose fundamental frequencies are in the ratio of 1 : 2 : 3.

(a) 30 cm and 90 cm

(b) 40 cm and 80 cm

(c) 60 cm, 30 cm and 20 cm

(d) 30 cm and 60 cm

**Question 25:
**A sound source is moving towards stationary listener with 1/10th of the speed of sound. The ratio of apparent to real frequency is

(a) 11/10

(b) (11/10)

^{2}

(c) (9/10)

^{2}

(d) 10/9

**Question 26:
**A car is moving towards a high cliff. The car driver sounds a horn of frequency f. The reflected sound heard by the driver has a frequency 2f. If v be the velocity of sound, then the velocity of the car, in the same velocity units will be

(a) v/√2

(b) v/3

(c) v/4

(d) v/2

**Question 27:
**The frequency changes by 10% as the source approaches a stationary observer with constant speed Vs. What would be the percentage change in frequency as the source recedes the observer with the same speed? Given, that Vs << v (v = speed of sound in air)

(a) 14.3%

(b) 20%

(c) 16.7%

(d) 10%

**Question 28:
**Two sound waves with wavelengths 5.0 m and 5.5 m respectively, each propagate in a gas with velocity 330 ms

^{-1}. We expect the following number of beats per second

(a) 12

(b) 0

(c) 1

(d) 6

**Question 29:
**A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distance of 2 m and 3 m respectively, from the source. The ratio of the intensities of the waves at P and Q is

(a) 9: 4

(b) 2:3

(c) 3 : 2

(d) 4 : 9

**Question 30:
**Velocity of sound in the atmosphere of a planet is 500 ms

^{-1}. The minimum distance between the source of sound and the obstacle to hear the echo should be

(a) 17 m

(b) 20 m

(c) 25 m

(d) 50 m

**Question 31:
**A sound absorber attenuates the sound level by 20 dB. The intensity decreases by a factor of

(a) 1000

(b) 10000

(c) 10

(d) 100

**Question 32:
**A sound wave y = A sin (ωt – kx) is propagating through a medium of density ρ. What is the sound energy per unit volume?

(a) 1/2 ρA

^{2}ω

^{2}

(b) ρA

^{2}ω

^{2}

(c) 2ρA

^{2}ω

^{2}

(d) 4ρA

^{2}ω

^{2}

**Question 33:
**If two waves of wavelengths 50 cm and 51 cm produced 12 beats/s, the velocity of sound is

(a) 360 ms

^{-1}

(b) 306 ms

^{-1}

(c) 331 ms

^{-1}

(d) 340 ms

^{-1}

**Question 34:
**Two wave of wavelengths 99 cm and 100 cm both travelling with velocity 396 ms

^{-1}are made of interfere. The number of beats produced by them per second are

(a) 1

(b) 2

(c) 4

(d) 8

**Question 35:
**A train is approaching the platform with a speed of 4 ms

^{-1}. Another train is leaving the platform with the same speed. The velocity of sound is 320ms

^{-1}. If both the trains sound their whistles at frequency 280 Hz, the number of beats heard per second will be

(a) 6

(b) 7

(c) 8

(d) 10

**Question 36:
**Two tuning forks P and Q when set vibrating, give 4 beats/s. If a prong of the fork P is filed, the beats are reduced to 2/s. What is frequency of P, if that of Q is 250 Hz?

(a) 246 Hz

(b) 250 Hz

(c) 254 Hz

(d) 252 Hz

**Question 37:
**

**Question 38:
**A wave pulse in a thin string is incident on a thick string as shown in figure. If joint is at P, then the form of relfected and transmitted pulses is

**Question 39:
**A boy is sitting on a swing and blowing a whistle at a frequency of 1000 Hz. The swing is moving to an angle of 30° from the vertical. The boy is at 2m from the point of support of swing and a girl stands in front of swing. Then, the maximun frequency she will hear is (given velocity of sound =330 m/s)

(a) 1000 Hz

(b) 1001 Hz

(c) 1007 Hz

(d) 1011 Hz

**Question 40:
**With propagation of longitudinal waves through a medium, the quantity transmitted is

(a) matter

(b) energy

(c) energy and matter

(d) energy, matter and momentum

**Question 41:
**The graph between distance of source and observer and apparent frequency in the case of Doppler’s effect will be

**Direction (Q. Nos. 42-44):** In each of the following questions a statement of Assertion is given followed by a corresponding statement of Reason just below it. Of the statements mark the correct answer as

(a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion

(b) If both Assertion.and Reason are true but the Reason is not the correct explanation of the Assertion

(c) If Assertion is true but Reason is false

(d) If both Assertion and Reason are false

**Question 42:
Assertion (A): **Solids can support both longitudinal and transverse waves, but only longitudinal waves can propagate in gases.

**Solids possess two types of elasticity.**

Reason (R):

Reason (R):

**Question 43:
Assertion (A): **A tuning fork is in resonance with a closed pipe. But the same tuning fork cannot be in resonance with an open pipe of the same length.

**The same tuning fork will not be in resonance with open pipe of same length due to end correction of pipe.**

Reason (R):

Reason (R):

**Question 44:
Assertion (A): **In a stationary wave, there is not transfer of energy.

**There is no outward motion of the disturbance from one particle to adjoining particle in a stationary wave.**

Reason (R):

Reason (R):

**Question 45:
**The fundamental frequency of a closed organ pipe of length 20 cm is equal to the second overtone of an organ pipe open at both the ends. The length of organ pipe open at both the ends is

(a) 80 cm

(b) 100 cm

(c) 120 cm

(d) 140 cm

**Question 46:
**

**Question 47:
**The number of possible natural oscillations of air column in pipe closed at one end of length 85 cm whose frequencies lie below 1250 Hz are (velocity of sound.= 340 ms

^{-1})

(a) 4

(b) 5

(c) 7

(d) 6

**Question 48:
**A speeding motorcyclist sees traffic jam ahead of him. He slows down to 36 km/hour. He finds that traffic has eased and a car moving ahead of him at 18 km/h is honking at a frequency of 1392 Hz. If the speed of sound is 343 m/s, the frequency of the honk as heard by him will be

(a) 1332 Hz

(b) 1372 Hz

(c) 1412 Hz

(d) 1454 Hz

**Direction (Q. Nos. 49-50):** In each of the following questions a statement of Assertion is given followed by a corresponding statement of Reason just below it. Of the statements mark the correct answer as

(a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion

(b) If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion

(c) If Assertion is true but Reason is false

(d) If both Assertion and Reason are false

**Question 49:
Assertion (A): **Velocity of particles while crossing mean position (in stationary waves) varies from maximum at anti-nodes to zero at nodes.

**Amplitude of vibration at anti-nodes maximum and at nodes, the amplitude is zero and particles between two successive nodes cross the mean position together.**

Reason (R):

Reason (R):

**Question 50:
Assertion (A): **It is not possible to have interference between the waves produced by two violins.

**For interference of two waves, the phase difference between the waves must remain constant.**

Reason (R):

Reason (R):

**Question 51:
**When a string is divided into three segments of lengths l

_{1}, l

_{2}and l

_{3}, the fundamental frequencies of these three segments are ν

_{1},ν

_{2}and ν

_{3}, respectively. The original fundamental frequency (ν) of the string is

**Question 52:
**A transverse wave propagating on a stretched string of linear density 3 x10

^{-4}kgm

^{-1}is represented by the equation

y = 0.2sin(15x+60t)

where, x is in metres and t is in seconds. The tension in the string (in newton) is

(a) 0.24

(b) 0.48

(c) 1.20

(d) 1.80

**Question 53:
**The velocity of sound in air at NTP is 330 m/s. What will be its value when temperature is doubled and pressure is halved?

(a) 330 m/s

(b) 165 m/s

(c) 330 √2 m/s

(d) 320/√2 m/s

**Question 54:
**Two points on a travelling wave having frequency 500 Hz and velocity 300 m/s are 60° out of phase, then the minimum distance between the two points is

(a) 0.2

(b) 0.1

(c) 0.5

(d) 0.4

**Question 55:
**Doppler’s effect is sound in addition of relative velocity between source and observer, also depends while source and observer or both are moving. Doppler effect in light depend only on the relative velocity of source and observer. The reason of this is

(a) Einstein mass-energy relation

(b) Einstein theory of relativity

(c) Photoelectric effect

(d) None of the above

**Question 56:
**

**Question 57:
**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

(a) Increases by a factor 20

(b) Increases by a factor 10

(c) Decreases by a factor 20

(d) Decreases by a factor 10

**Question 58:
**A source of sound S is moving with a velocity of 50 m/s towards a stationary observer. The observer measures the frequency of the source as 1000 Hz. What will be the apparent frequency of the source when it is moving away from the observer after crossing him? The velocity of the sound in the medium is 350 m/s.

(a) 750 Hz

(b) 857 Hz

(c) 1143 Hz

(d) 1333 Hz

**Question 59:
**The wave of wavelength 5900 A emitted by any atom or molecule must have some finite total length which is known as coherence length. For sodium light, this length is 2.4 cm. The number of oscillations in this length will be

(a) 4.068 x 10

^{8}

(b) 4.068×10

^{4}

(c) 4.068×10

^{6}

(d) 4.068×10

^{5}

**Question 60:
Assertion (A): **The fundamental frequency of an open organ pipe increases as the temperature is increased.

**As the temperature increases, the velocity of sound increases more rapidly than length of the pipe.**

Reason (R):

Reason (R):

(a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion

(b) If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion

(c) If Assertion is true but Reason is false

(d) If both Assertion and Reason are false

### Answers:

### Hints And Solutions: