# MCQs For NCERT Class 11 Physics Chapter 15 Waves

Please refer to the MCQ Questions for Class 11 Physics Chapter 15 Waves with Answers. The following Waves Class 11 Physics MCQ Questions have been designed based on the latest syllabus and examination pattern for Class 11. Our experts have designed MCQ Questions for Class 11 Physics with Answers for all chapters in your NCERT Class 11 Physics book.

## Waves Class 11 MCQ Questions with Answers

See below Waves Class 11 Physics MCQ Questions, solve the questions and compare your answers with the solutions provided below.

Question. Frequencies of sound produced from an organ pipe open at both ends are
(a) only fundamental note
(b) only even harmonics
(c) only odd harmonics
(d) even and odd harmonics

D

Question. The fundamental frequency of an organ pipe is 512 Hz. If its length is increased, then frequency will
(a) decrease
(b) increase
(c) remains same
(d) cannot be predicted

A

Question. The property of a medium necessary for wave propagation is
(a) inertia
(b) elasticity
(c) low resistance
(d) All of the above

D

Question Doppler’s effect is not applicable for
(a) audio waves
(b) electromagnetic waves
(c) shock waves
(d) None of these

C

Question. Two sound waves of equal intensity I produce beats. The maximum intensity of sound produced in beats will be
(a) I
(b) 2I
(c) 3I
(d) 4I

D

Question. Two sinusoidal plane waves of same frequency having intensities I0 and 4 I0 are travelling in the same direction. The resultant intensity at a point at which waves meet with a phase difference of zero radian is
(a) I0
(b) 5 I0
(c) 9 I0
(d) 3 I0

C

Question. If the intensities of two interfering waves be I1 and I2, the contrast between maximum and minimum intensity is maximum, when
(a) I1 > > I2
(b) I1 << I2
(c) I1 = I2
(d) either I1 or I2 is zero

C

Question. Sound waves of length l travelling with velocity v in a medium enter into another medium in which their velocity is 4 v. The wavelength in 2nd medium is
(a) 4λ
(b) l
(c) l/4
(d) 16 l

A

Question. Sound waves are not transmitted to long distances because,
(a) they are absorbed by the atmosphere
(b) they have constant frequency
(c) the height of antenna required, should be very high
(d) velocity of sound waves is very less

A

Question. What is the effect of increase in temperature on the frequency of sound produced by an organ pipe?
(a) increases
(b) decreases
(c) no effect
(d) erratic change

A

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

B

Question. The equation Y = 0.02 sin (500pt) 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

A

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

C

Question. Shock waves are produced by objects
(a) carrying electric charge and vibrating
(b) vibrating with frequency greater than 20000 Hz
(c) vibrating with very large amplitude
(d) moving with a speed greater than that of sound in the medium

D

Question. The speed of sound in a medium depends on
(a) the elastic property but not on the inertia property
(b) the inertia property but not on the elastic property
(c) the elastic property as well as the inertia property
(d) neither the elastic property nor the inertia property

C

Question. Consider the three waves z1, z2 and z3 as
z1 = A sin (kx – wt)
z2 = A sin (kx + wt)
z3 = A sin (ky – wt)
Which of the following represents a standing wave?
(a) z1 + z2
(b) z2 + z3
(c) z3 + z1
(d) z1 + z2 + z3

A

Question. Three transverse waves are represented by
y1 = A cos (kx – wt)
y2 = A cos (kx + wt)
y3 = Acos (ky – wt)
The combination of waves which can produce stationary
waves is
(a) y1 and y2
(b) y2 and y3
(c) y1 and y3
(d) y1, y2 and y3

A

Question. Which of the following changes at an antinode in a stationary wave?
(a) Density only
(b) Pressure only
(c) Both pressure and density
(d) Neither pressure nor density

D

Question. A wave y = a sin (wt – kx) on a string meets with another wave producing a node at x = 0. Then the equation of the unknown wave is
(a) y = a sin (wt + kx)
(b) y = –a sin (wt + kx)
(c) y = a sin (wt – kx)
(d) y = –a sin (wt – kx)

B

Question. A uniform wire of length 20 m and weighing 5 kg hangs vertically. If g = 10 m/s2, 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

A

Question. The fundamental frequency of an open organ pipe is 300 Hz. The first overtone of this pipe has same frequency as first overtone of a closed organ pipe. If speed of sound is 330 m/s, then the length of closed organ pipe is
(a) 41 cm
(b) 37 cm
(c) 31 cm
(d) 80 cm

A

Question. A pipe closed at one end produces a fundamental note of 412 Hz. It is cut into two pieces of equal length. the fundamental frequencies produced by the two pieces are
(a) 206 Hz, 412 Hz
(b) 824 Hz, 1648 Hz
(c) 412 Hz, 824 Hz
(d) 206 Hz, 824 Hz

B

Question. A train has just completed U-curve in a track which is a semicircle.
The engine is at the forward end of the semi-circular part of the track while the last carriage is at the rear end of the semi circular track. The driver blows a whistle of frequency 200 Hz. Velocity of sound is 340 m/sec Then the apparent frequency as observed by a passenger in the middle of the train, when the speed of the train is 30 m/sec is
(a) 181 Hz
(b) 200 Hz
(c) 188 Hz
(d) 210 Hz

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

C

Question. If two waves of same frequency and same amplitude, on superposition, produce a resultant disturbance of the same amplitude, the wave differ in phase by
(a) p
(b) 2 p/3
(c) Zero
(d) p/3

B

Question. Two tones of frequencies n1 and n2 are sounded together. The beats can be heard distinctly when
(a) 10 < (n1 – n2) < 20
(b) 5 < (n1 – n2) > 20
(c) 5 < (n1 – n2) < 20
(d) 0 < (n1 – n2) < 10

D

Question. The equation of a spherical progressive wave is
(a) y = a sin wt
(b) y = a sin (wt – kr)
(c) y = a/√sin ( t kr)
(d) y = a/rsin ( t kr)

D

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

B

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

B

Question. A person standing symmetrically between two cliffs claps his hands and starts hearing a series of echoes at intervals of 1 sec. If speed of sound in air is 340 m/s, the distance between the parallel cliffs must be
(a) 340 m
(b) 680 m
(c) 1020 m
(d) 170 m

A

Question. An echo repeats two syllables. If the velocity of sound is 330 m/s, then the distance of the reflecting surface is
(a) 66.0 m
(b) 33.0 m
(c) 99.0 m
(d) 16.5 m

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

C

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

D

Question. If the ratio of maximum to minimum intensity in beats is 49, then the ratio of amplitudes of two progressive wave trains is
(a) 7 : 1
(b) 4 : 3
(c) 49 : 1
(d) 16 : 9

B

Question. There are three sources of sound of equal intensities and frequencies 400, 401 and 402 vibrations per second. The number of beats/sec is
(a) 0
(b) 1
(c) 3
(d) 2

B

Question. A fork of unknown frequency gives four beats/sec when sounded with another of frequency 256. The fork is now loaded with a piece of wax and again four beats/sec are heard. Then the frequency of the unknown fork is
(a) 256 Hz
(b) 252 Hz
(c) 264 Hz
(d) 260 Hz

D

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

A

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 × 107 m/sec
(b) 6 × 106 m/sec
(c) 6 × 105 m/sec
(d) 6 × 104 m/sec

C

Question. In a resonance column, first and second resonance are obtained at depths 22.7 cm and 70.2 cm. The third resonance will be obtained at a depth
(a) 117.7 cm
(b) 92.9 cm
(c) 115.5 cm
(d) 113.5 cm

A

Question. A fork of frequency 256 Hz resonates with a closed organ pipe of length 25.4 cm. If the length of pipe be increased by 2 mm, the number of beats/sec. will be
(a) 4
(b) 1
(c) 2
(d) 3

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 × 1014 Hz. The observed frequency of this spectral line is
(a) 4.5 × 108 Hz
(b) 4.485 × 1014 Hz
(c) 4.515 × 1014 Hz
(d) 4.5 × 1014 Hz

B

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

B

Question. A wave disturbance in a medium is described by y(x+t) = 0.02cos(50πt + π/2) where x and y are in metre and t is in second. Which of the following is correct?
(a) A node occurs at x = 0.15 m
(b) An antinode occurs at x = 0.3 m
(c) The speed wave is 5 ms–1
(d) The wavelength is 0.3 m

C

Question. Two waves represented by y1 = a sinwt and y2 = a sin(wt + f) 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

C

Question. The equation y = Asin2 (kx -wt) represents a wave with
(a) amplitude A, frequency w/ 2p
(b) amplitude A/2, frequency w/ p
(c) amplitude 2A, frequency w/ 4p
(d) it does not represent a wave motion

B

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

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

C

Question. The speed of sound in oxygen (O2) at a certain temperature is 460 ms–1. The speed of sound in helium (He) at the same temperature will be (assume both gases to be ideal)
(a) 460 ms–1
(b) 500 ms–1
(c) 650 ms–1
(d) 330 ms–1

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

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) 1012 dB
(b) 12 dB
(c) 240 dB
(d) 120 dB

D

Question. In expressing sound intensity, we take 10–12 W m–2 as the reference level. For ordinary conversation, the intensity level is about 10–6 W m–2. Expressed in decibel, this is
(a) 106
(b) 6
(c) 60
(d) loge (106)