Please refer to MCQ Questions Chapter 15 Waves Class 11 Physics with answers provided below. These multiple-choice questions have been developed based on the latest NCERT book for class 11 Physics issued for the current academic year. We have provided MCQ Questions for Class 11 Physics for all chapters on our website. Students should learn the objective based questions for Chapter 15 Waves in Class 11 Physics provided below to get more marks in exams.

**Chapter 15 Waves MCQ Questions**

Please refer to the following **Chapter 15 Waves MCQ Questions Class 11 Physics** with solutions for all important topics in the chapter.

**MCQ Questions Answers for Chapter 15 Waves Class 11 Physics**

**Question.** The two nearest harmonics of a tube closed at one end and open at other end are 220 Hz and 260 Hz. What is the fundamental frequency of the system?

(a) 20 Hz

(b) 30 Hz

(c) 40 Hz

(d) 10 Hz

**Answer**

A

**Question.****A speeding motorcyclist sees trafic 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/hour is honking at a frequency of 1392 Hz. If the speeds 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) 1464 Hz

**Answer**

C

**Question.** A source of unknown frequency gives 4 beats/s, when sounded with a source of known frequency 250 Hz. The second harmonic of the source of unknown frequency gives five beats per second, when sounded with a source of frequency 513 Hz. The unknown frequency is

(a) 246 Hz

(b) 240 Hz

(c) 260 Hz

(d) 254 Hz

**Answer**

D

**Question.** A sound wave is passing through air column in the form of compression and rarefaction. In consecutive compressions and rarefactions,

(a) density remains constant

(b) Boyle’s law is obeyed

(c) bulk modulus of air oscillates

(d) there is no transfer of heat

**Answer**

D

**Question.****Speed of sound wave in air**

(a) is independent of temperature

(b) increases with pressure

(c) increases with increase in humidity

(d) decreases with increase in humidity

**Answer**

C

**Question.** Two sources of sound placed close to each other are emitting progressive waves given by y_{1} = 4 sin 600 πt and y_{2} = 5 sin 608 πt. An observer located near these two sources of sound will hear

(a) 4 beats per second with intensity ratio 25 : 16 between waxing and waning.

(b) 8 beats per second with intensity ratio 25 : 16 between waxing and waning

(c) 8 beats per second with intensity ratio 81 : 1 between waxing and waning

(d) 4 beats per second with intensity ratio 81 : 1 between waxing and waning

**Answer**

D

**Question.** Two waves are represented by the equations y_{1} = a sin (ϖt + kx + 0.57) m and y_{2} = a cos (ϖt + kx) m, where x is in meter and t in sec. The phase difference between them is

(a) 1.0 radian

(b) 1.25 radian

(c) 1.57 radian

(d) 0.57 radian

**Answer**

A

**Question.** The phase difference between two waves, represented by**y _{1} = 10^{–6 }sin{100 t + (x/50) + 0.5} m**

**y**

_{2}= 10^{–6}cos{100 t + (x/50)} m**where x is expressed in metres and t is expressed in seconds, is approximately**

(a) 1.5 radians

(b) 1.07 radians

(c) 2.07 radians

(d) 0.5 radians

**Answer**

B

**Question.****Wave pulse on a string shown in figure is moving to the right without changing shape. Consider two particles at positions x _{1} = 1.5m and x_{2} = 2.5m. Their transverse velocities at the moment shown in figure are along directions**

(a) positive y-axis and positive y-axis respectively

(b) negative y-axis and positive y-axis respectively

(c) positive y-axis and negative y-axis respectively

(d) negative y-axis and negative y-axis respectively

**Answer**

B

**Question.** A source X of unknown frequency produces 8 beats per second with a source of 250 Hz and 12 beats per second with a source of 270 Hz. The frequency of the source X is

(a) 242 Hz

(b) 258 Hz

(c) 282 Hz

(d) 262 Hz

**Answer**

B

**Question.****A source of sound is travelling at 100/3 m s ^{–1} along a road, towards a point A. When the source is 3 m away from A, a person standing at a point O on a road perpendicular to the track hears a sound of frequency n’. The distance of O from A at that time is 4 m. If the original frequency is 640 Hz, then the value of n’ is (given : velocity of sound = 340 m s^{–1})**

(a) 620 Hz

(b) 680 Hz

(c) 720 Hz

(d) 840 Hz

**Answer**

B

**Question.****A person carrying a whistle emitting continuously a note of 272 Hz is running towards a reflecting surface with a speed of 18 km h ^{–1}. The speed of sound in air is 345 m s^{–1}. The number of beats heard by him is**

(a) 4

(b) 6

(c) 8

(d) zero

**Answer**

C

**Question.** An organ pipe, open from both end produces 5 beats per second when vibrated with a source of frequency 200 Hz. The second harmonic of the same pipes produces 10 beats per second with a source of frequency 420 Hz. The fundamental frequency of organ pipe is

(a) 195 Hz

(b) 205 Hz

(c) 190 Hz

(d) 210 Hz

**Answer**

B

**Question.** The displacement of a particle varies according to the relation x = 4(cos πt + sin πt). The amplitude of the particle is

(a) – 4 m

(b) 4 m

(c) 4√2m

(d) 8 m

**Answer**

C

**Question.****If two tuning forks A and B are sounded together, they produce 4 beats per sec. A is then slightly loaded with wax and same no. of beats/sec. are produced again. If frequency of A is 256, the frequency of B would be**

(a) 250

(b) 262

(c) 252

(d) 260

**Answer**

C

**Question.****A closed pipe and an open pipe have their first overtones identical in frequency. Their lengths are in the ratio**

(a) 1 : 2

(b) 2 : 3

(c) 3 : 4

(d) 4 : 5

**Answer**

C

**Question.** A toothed wheel is rotating at 240 rpm and a post card is held against the teeth. If the pitch of the tone is 256 Hz, then the number of teeth on the rotating wheel is

(a) 256

(b) 128

(c) 64

(d) 32

**Answer**

C

**Question.****The equation Y = 0.02 sin (500πt) cos (4.5 x) represents**

(a) progressive wave of frequency 250 Hz along x-axis

(b) a stationary wave of wavelength 1.4 m

(c) a transverse progressive wave of amplitude 0.02 m

(d) progressive wave of speed of about 350 m s^{–1}

**Answer**

B

**Question.** Two waves represented by y_{1} = a sinwt and y_{2} = a sin(wt + Φ) with Φ = π/2 are superposed at any point at a particular instant. The resultant amplitude is

(a) a

(b) 4a

(c) √2a

(d) zero

**Answer**

C

**Question.****A distant star which is moving away with a velocity of 106 m/sec is emitting a red line of frequency 4.5 × 10 ^{14} Hz. The observed frequency of this spectral line is**

(a) 4.5 × 10

^{8}Hz

(b) 4.485 × 10

^{14 }Hz

(c) 4.515 × 10

^{14}Hz

(d) 4.5 × 10

^{14}Hz

**Answer**

B

**Question.****If there are six loops for 1 m length in transverse mode of Melde’s experiment., the no. of loops in longitudinal mode under otherwise identical conditions would be**

(a) 3

(b) 6

(c) 12

(d) 8

**Answer**

A

**Question.****At room temperaturre, velocity of sound in air at 10 atmospheric pressure and at 1 atmospheric pressure will be in the ratio**

(a) 10 : 1

(b) 1 : 10

(c) 1 : 1

(d) cannot say

**Answer**

C

**Question.****The velocity of sound in air is 330 m/s. The r.m.s. velocity of air molecules (g = 1.4) is approximately equal to**

(a) 400 m/s

(b) 471.4 m/s

(c) 231 m/s

(d) 462 m/s

**Answer**

B

**Question.****The equation y a sin 2π/λ (vt – x) = is expression for**

(a) stationary wave of single frequency along x-axis

(b) a simple harmonic motion

(c) a progressive wave of single frequency along x-axis

(d) the resultant of two SHMs of slightly different frequencies

**Answer**

C

**Question.** When a string is divided into three segments of length l_{1}, l_{2}, and l_{3} the fundamental frequencies of these three segments are v_{1}, v_{2} and v_{3} respectively. The original fundamental frequency (v) of the string is

**Answer**

C

**Question.** The velocity of sound in hydrogen is 1224 m/s. Its velocity in a mixture of hydrogen and oxygen containing 4 parts by volume of hydrogen and 1 part oxygen is

(a) 1224 m/s

(b) 612 m/s

(c) 2448 m/s

(d) 306 m/s

**Answer**

B

**Question.** A series of ocean waves, each 5.0 m from crest to crest, moving past the observer at a rate of 2 waves per second, what is the velocity of ocean waves?

(a) 2.5 m/s

(b) 5.0 m/s

(c) 8.0 m/s

(d) 10.0 m/s

**Answer**

D

**Question.****The apparent wavelength of the light from a star moving away from the earth is 0.2% more than its actual wavelength. Then the velocity of the star is**

(a) 6 × 10^{7 }m/sec

(b) 6 × 10^{6} m/sec

(c) 6 × 10^{5 }m/sec

(d) 6 × 10^{4} m/sec

**Answer**

C

**Question.** The speed of sound in air under ordinary conditions is around 330 m s^{–1}. The speed of sound in hydrogen under similar conditions will be (in m s^{–1}) nearest to

(a) 330

(b) 1200

(c) 600

(d) 900

**Answer**

B

**Question.** If the speed of a transverse wave on a stretched string of length 1 m is 60 m/s, what is the fundamental frequency of vibration?

(a) 10 Hz

(b) 30 Hz

(c) 40 Hz

(d) 70 Hz

**Answer**

B

**Question.** The intensity level of sound wave is said to be 4 decibel. If the intensity of wave is doubled, then the intensity level of sound as expressed in decibel would be

(a) 8

(b) 16

(c) 7

(d) 14

**Answer**

C

**Question.** When a tuning fork vibrates with 1.0 m or 1.05 m long wire of a sonometer, 5 beats per second are produced in each case. What will be the frequency of the tuning fork?

(a) 195

(b) 200

(c) 205

(d) 210

**Answer**

C

**Question.** The threshold of hearing for the human ear is 10^{–12 }W m^{–2}. This is taken as the standard level. The intensity of sound is 1 Wm^{–2}. It has intensity (in dB).

(a) 10^{12} dB

(b) 12 dB

(c) 240 dB

(d) 120 dB

**Answer**

D

**Question.** A uniform wire of length 20 m and weighing 5 kg hangs vertically. If g = 10 m/s^{2}, then the speed of transverse waves in the middle of the wire is

(a) 10 m/s

(b) 10√2 m/s

(c) 4 m/s

(d) zero

**Answer**

A

**Question.** Two waves of wavelengths 99 cm and 100 cm both travelling with velocity 396 m/s are made to interfere. The number of beats produced by them per second is

(a) 1

(b) 2

(c) 4

(d) 8

**Answer**

C

**Question.****A progressive sound wave of frequency 500 Hz is travelling through air with a speed of 350 ms ^{–1}. A compression maximum appears at a place at a given instant. The minimum time interval after which the rarefraction maximum occurs at the same point, is**

**Answer**

D

**Question.****In the sonometer experiment, a tuning fork of frequency 256 Hz is in resonance with 0.4 m length of the wire when the iron load attached to free end of wire is 2 kg. If the load is immersed in water, the length of the wire in resonance would be (specific gravity of iron = 8)**

(a) 0.37 m

(b) 0.43 m

(c) 0.31 m

(d) 0.2 m

**Answer**

A

**Question.** The equation of a stationary wave is : y = 4 sin (πx/15) cos (96 πt) . The distance between a node and its next antinode is

(a) 7.5 units

(b) 1.5 units

(c) 22.5 units

(d) 30 units

**Answer**

A

**Question.** An isotropic point source S of sound emits constant power. Two points A and B separated by a distance r are situated near the source as shown in figure. The difference of the intensity level of sound at the points A and B is about

(a) 3 dB

(b) 2 dB

(c) 6 dB

(d) 12 dB

**Answer**

C

**Question.****The transverse wave represented by the equation**

**Answer**

C

**Question.****Two vibrating tuning forks produce progressive waves given by Y _{1} = 4 sin 500 πt and Y_{2} = 2 sin 506 πt. Number of beats produced per minute is**

(a) 360

(b) 180

(c) 60

(d) 3

**Answer**

B

**Question.** 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) decreases by a factor 10

(b) increases by a factor 20

(c) increases by a factor 10

(d) decreases by a factor 20

**Answer**

C

**Question.****Water waves produced by a motorboat sailing in water are**

(a) neither longitudinal nor transverse

(b) both longitudinal and transverse

(c) only longitudinal

(d) only transverse

**Answer**

B

**Question.** Change in temperature of the medium changes

(a) frequency of sound waves

(b) amplitude of sound waves

(c) wavelength of sound waves

(d) loudness of sound waves

**Answer**

C

**Question.****Equation of a plane progressive wave is given by**

**Answer**

B

**Question.****A wave travelling in the +ve x-direction having displacement along y-direction as 1m, wavelength 2π m and frequency 1/π Hz is represented by**

(a) y = sin (2πx – 2πt)

(b) y = sin (10πx – 20πt)

(c) y = sin (2πx + 2πt)

(d) y = sin (x – 2t)

**Answer**

D

**Question.****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) 100 cm

(b) 120 cm

(c) 140 cm

(d) 80 cm

**Answer**

B

**Question.** Two cars moving in opposite directions approach each other with speed of 22 m/s and 16.5 m/s respectively. The driver of the first car blows a horn having a frequency 400 Hz. The frequency heard by the driver of the second car is [velocity of sound 340 m/s] :-

(a) 361 Hz

(b) 411 Hz

(c) 448 Hz

(d) 350 Hz

**Answer**

C

**Question.****An air column, closed at one end and open at the other, resonates with a tuning fork when the smallest length of the column is 50 cm. The next larger length of the column resonating with the same tuning fork is :**

(a) 66.7 cm

(b) 100 cm

(c) 150 cm

(d) 200 cm

**Answer**

C

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