CBSE Class 11 Physics Waves Worksheet

Question. The sound intensity level at a point 4 m from the point source is 10 dB, then the sound level at a distance 2 m from the same source will be

(1) 26 dB

(2) 16 dB

(3) 23 dB

(4) 32 dB

Answer (2)

Question. Select the correct statement about the reflection and refraction of a wave at the interface between the medium 1 and 2 the

(1) Reflected wave has a phase change of π

(2) Wavelength of reflected wave is less than that of incident wave

(3) Frequency of transmitted wave is same as that of incident wave

(4) Frequency of wave changes as per nature of boundary

Answer (3)
 

Question. The speed of sound in air is independent from its

(1) Amplitude

(2) Frequency

(3) Phase

(4) All of these

Answer (4)

Question. When a wave propagating through a medium encounters a change in medium, then which of the following property remains same?

(1) Speed

(2) Amplitude

(3) Frequency

(4) Wavelength

Answer (3)

Question. The phenomenon of sound propagation in air is

(1) An isothermal process

(2) An adiabatic process

(3) An isobaric process

(4) An isochoric process

Answer (2)

Question. If at STP, velocity of sound in a gas (π = 1.5) is 600 m/s, the r.m.s. velocity of the gas molecules at STP will be

(1) 400 m/s

(2) 600 m/s

(3) 600  m/s²

(4) 300  m/s²

Answer (3)

Question. In a stretched string,

(1) Only transverse waves can exist

(2) Only longitudinal waves can exist

(3) Both transverse and longitudinal waves can exist

(4) None of these

Answer (1)

Question. Two strings of same material are stretched to the same tension. If their radii are in the ratio 1 : 2, then respective wave velocities in them will be in ratio

(1) 4 : 1

(2) 2 : 1

(3) 1 : 2

(4) 1 : 4

Answer (2)

Question.  A wave is represented by the equation y = A sin (10πx +15πt + π/6) where x is in metre and t in second. The expression represents

(1) A wave travelling in negative x-direction with a velocity of 1.5 m/s

(2) A wave travelling in positive x direction with a velocity of 1.5 m/s

(3) A wave traveling in positive x-direction with wavelength 0.2 m

(4) A wave travelling in negative x-direction with a velocity of 150 m/s

Answer (1)

Question.  The tension in a wire is decreased by 19%. The percentage decrease in frequency will be

(1) 0.19%

(2) 10%

(3) 19%

(4) 0.9%

Answer (2)

Question.  In a simple harmonic wave, minimum distance between particles in same phase always having same velocity, is

(1) λ/4

(2) λ/3

(3) λ/2

(4) λ

Answer (4)

Question. A transverse wave travels along x-axis. The particles of medium move

(1) Along x-axis

(2) Along y-axis

(3) Along z-axis

(4) Either along y-axis or z-axis

Answer (4)

Question.  The tones that are separated by three octaves have a frequency ratio of

(1) 3

(2) 6

(3) 8

(4) 16

Answer (3)

Question. Which of the following phenomenon cannot take place with sound waves?

(1) Polarisation

(2) Refraction

(3) Diffraction

(4) Reflection

Answer (1)

Question.  In a stationary wave

(1) Strain is maximum at nodes

(2) Strain is minimum at nodes

(3) Strain is maximum at antinodes

(4) Amplitude is zero at all points

Answer (1)

Question. A 12 m long vibrating string has the speed of wave 48 m/s. To what frequency it will resonate?

(1) 2 cps

(2) 4 cps

(3) 6 cps

(4) All of these

Answer (4)

Question. The waves which cannot travel without medium are

(1) X-rays

(2) Radio waves

(3) Light waves

(4) Sound waves

Answer (4)

Question. A certain string will resonant to several frequencies, the lowest of which is 200 cps. What are the next three higher frequencies to which it resonants?

(1) 400, 600, 800

(2) 300, 400, 500

(3) 100, 150, 200

(4) 200, 250, 300

Answer (1)

Question. An aluminium rod having a length 100 cm is clamped at its middle point and set into longitudinal vibrations.Let the rod vibrate in its fundamental mode. The density of aluminium is 2600 kg/m3 and its Young’s modulus is 7.8 × 1010 N/m². The frequency of the sound produced is

(1) 1250 Hz

(2) 2740 Hz

(3) 2350 Hz

(4) 1685 Hz

Answer (2)

Question. A tuning fork of unknown frequency produces 4 beats per second when sounded with another tuning fork of frequency 254 Hz. It gives the same number of beats per second when unknown tuning fork loaded with wax. The unknown frequency before loading with wax is

(1) 258

(2) 254

(3) 250

(4) Can’t be determined

Answer (1)

Question. A wire of length one metre under a certain initial tension emits a sound of fundamental frequency 256 Hz. When the tension is increased by 1 kg wt, the frequency of the fundamental node increases to 320 Hz. The initial tension is

(1) 3/4 kg wt

(2) 4/3 kg wt

(3) 16/9 kg wt

(4) 20/9 kg wt

Answer (3)

Question. The pitch of an organ pipe is highest when the pipe is filled with

(1) Air

(2) Hydrogen

(3) Oxygen

(4) Carbon dioxide

Answer (2)

Question. A cylindrical tube, open at both ends, has a fundamental frequency f in air. The tube is dipped vertically in water so that half of it is in water. The fundamental frequency of the air column is now

(1) f/2

(2) 3f/4

(3) f

(4) 2 f

Answer (3)

Question. A man standing on a platform observes that the frequency of the sound of a whistle emitted by a train drops by 140 Hz. If the velocity of sound in air is 330 m/s and the speed of the train is 70 m/s, the frequency of the whistle is

(1) 571 Hz

(2) 800 Hz

(3) 400 Hz

(4) 260 Hz

Answer (2)

Question. For a certain organ pipe, three successive resonance frequencies are observed at 425, 595, and 765, Hz respectively, Taking the speed of sound in air to be 340 m/s the fundamental frequency of the pipe (in Hz) is

(1) 425

(2) 170

(3) 85

(4) 245

Answer (3)

Question. The length of a sonometer wire is 0.75 m and density 9 × 103 Kg/m3. It can bear a stress of 8.1 × 108 N/m² without exceeding the elastic limit. The fundamental frequency that can be produced in the wire, is

(1) 200 Hz

(2) 150 Hz

(3) 600 Hz

(4) 450 Hz

Answer (1)

Question. A tuning fork vibrating with a sonometer having a wire of length 20 cm produces 5 beats per second. The beats frequency does not change if the length of the wire is changed to 21 cm. The frequency of the tuning fork must be

(1) 200 Hz

(2) 210 Hz

(3) 205 Hz

(4) 215 Hz

Answer (3)

Question. A closed pipe of length 10 cm has its fundamental frequency half that of the second overtone of an open pipe.The length of the open pipe

(1) 10 cm

(2) 20 cm

(3) 30 cm

(4) 40 cm

Answer (3)

Question. In resonance tube two successive positions of resonance are obtained at 15 cm and 48 cm. If the frequency of the fork is 500 cps, the velocity of sound is

(1) 330 m/s

(2) 300 m/s

(3) 1000 m/s

(4) 360 m/s

Answer (1)

Question. During superposition of two waves of nearly equal frequencies, beats frequency is defined as the

(1) Sum of frequencies of interfering waves

(2) Number of times the resultant intensity becomes maximum or minimum in one second

(3) Average of frequencies of interfering waves

(4) Number of times the resultant amplitude becomes maximum or minimum in one second

Answer (2)

Question. The string of a violin has a frequency of 440 cps. If the violin string is shortened by one fifth, its frequency will be changed to

(1) 440 cps

(2) 880 cps

(3) 550 cps

(4) 2200 cps

Answer (3)

Question. Ten tuning forks are arranged in increasing order of frequency in such a way that any two consecutive tuning forks produce 4 beats per second. The highest frequency is twice that of the lowest. Possible highest and lowest frequencies (in Hz) are

(1) 80 and 40

(2) 100 and 50

(3) 44 and 22

(4) 72 and 36

Answer (4)

Question. A tuning fork and an air column whose temperature is 51°C produce 4 beats in one second, when sounded together. When the temperature of air column decreases the number of beats per second decreases. When the temperature remains 16°C only one beat per second is produced. The frequency of the tuning fork is

(1) 100 Hz

(2) 75 Hz

(3) 150 Hz

(4) 50 Hz

Answer (4)

Question. In case of closed pipe which harmonic the p ^th overtone will be

(1) 2p + 1

(2) 2p – 1

(3) p + 1

(4) p – 1

Answer (1)

Question. The displacement at a point due to two waves are y₁= 4sin(500πt) and y₂= 2sin(506πt). The result due to their superposition will be

(1) 3 beats per second with intensity relation between maxima and minima equal to 2

(2) 3 beats per second with intensity relation between maxima and minima equal to 9

(3) 6 beats per second with intensity relation between maxima and minima equal to 2

(4) 6 beats per second with intensity relation between maxima and minima equal to 9

Answer (2)

Question. Which one of the following represents a wave?

(1) y = A sin (ωt – kx)

(2) y = A cos2 (at – bx + c) + A sin²(at – bx + c)

(3) y = A sin kx

(4) y = A sin ωt

Answer (1)

Question. If in a stationary wave the amplitude corresponding to antinode is 4 cm, then the amplitude corresponding to a particle of medium located exactly midway between a node and an antinode is

(1) 2 cm

(2) 2 √2 cm

(3) √2 cm

(4) 1.5 cm

Answer (2)

Question. A sinusoidal wave of frequency 500 Hz has a speed of 350 m/s. The phase difference between two displacements at a certain point at times 1 m apart is

(1) π/4

(2) π/2

(3) π

(4) 3 π/2

Answer (3)

Question.What is the phase difference between the displacement wave and pressure wave in sound wave?

(1) Zero

(2) π/2

(3) π

(4) π/4

Answer (2)

Question.In a standing wave, all particles of the medium cross the mean position with

(1) Different speeds at different instants

(2) Different speeds at same instant

(3) Same speed at different instants

(4) Same speed at same instant

Answer (2)

Question.The driver of a car travelling with speed 30 m/s towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 m/s, the frequency of reflected sound as heard by driver is

(1) 500 Hz

(2) 550 Hz

(3) 555.5 Hz

(4) 720 Hz

Answer (4)

Question.The longitudinal wave can be observed in

(1) Elastic media

(2) Inelastic media

(3) Both (1) & (2)

(4) None of these

Answer (1)

Question.The ratio of intensities between two coherent sound sources is 4 : 1. The difference of loudness in dB between maximum and minimum intensities when they interfere in the space is

(1) 20 log₁₀(3)

(2) 10 log₁₀(2)

(3) 20 log₁₀(2)

(4) 10 log₁₀(3)

Answer (1)

Question.In a sinusoidal wave, the time required for a particular point to move from maximum displacement to zero displacement is 0.170 s. The frequency of wave is

(1) 0.73 Hz

(2) 0.36 Hz

(3) 1.47 Hz

(4) 2.94 Hz

Answer (3)

Question. A uniform string resonates with a tuning fork, at a maximum tension of 32 N. If it is divided into two segments by placing a wedge at a distance one-fourth of length from one end, then to resonance with same frequency the maximum value of tension for string will be

(1) 2 N

(2) 4 N

(3) 8 N

(4) 16 N

Answer (1)

Question.The intensity of sound reduces by 20% on passing through a glass slab. If sound of intensity I is made to cross through two such slabs, then the intensity of emergent sound will be

(1) 0.36 I

(2) 0.64 I

(3) 0.4 I

(4) 0.8 I

Answer (2)

Question.A stationary wave is represented by y = A sin (100t) cos (0.01x), where y and A are in millimetres, t is in second and x is in metre. The velocity of the constituent wave is

(1) 10⁴ m/s

(2) Not derivable

(3) 1 m/s

(4) 10² m/s

Answer (1)

Question.Standing waves are produced in 10 m long stretched string fixed at both ends. If the string vibrates in 5 segments and wave velocity is 20 m/s, the frequency is

(1) 5 Hz

(2) 10 Hz

(3) 2 Hz

(4) 4 Hz

Answer (1)

Question.The standing wave in a medium is expressed as y = 0.2 sin (0.8x) cos (3000t) m. The distance between any two consecutive points of minimum or maximum displacement is

(1) π/2 m

(2) π/4 m

(3) π/6 m

(4) None of these

Answer (4)

Question.The ratio of maximum particle velocity to wave velocity is [where symbols have their usual meanings]

(1) kA

(2) Aω

(3) kω

(4) ω/k

Answer (1)

Question.For a particular resonance tube, following are four of the six harmonics below 1000 Hz;
300, 600, 750 and 900 Hz
The two missing harmonics are

(1) 75, 150

(2) 150, 450

(3) 400, 800

(4) 250, 400

Answer (2)

Question.In a closed organ pipe of length 105 cm, standing waves are set up corresponding to third overtone. What distance from the closed end, a pressure node is formed?

(1) 5 cm

(2) 15 cm

(3) 25 cm

(4) 30 cm

Answer (2)

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

(1) 60 cm and 90 cm

(2) 30 cm and 60 cm

(3) 30 cm and 90 cm

(4) 40 cm and 80 cm

Answer (1)

Question. The two waves of the same frequency moving in the same direction give rise to

(1) Beats

(2) Interference

(3) Stationary waves

(4) None of these

Answer (2)

Question.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 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) 3500 Hz

(2) 4000 Hz

(3) 5000 Hz

(4) 3000 Hz

Answer (3)

Question.A vibrating tuning fork is moving slowly and uniformly in a horizontal circular path of radius 8 m. The shortest distance of an observer in same plane from the tuning fork is 9 m. The distance between the tuning fork and observer at the instant when apparent frequency becomes maximum is

(1) 9 m

(2) 25 m

(3) 15 m

(4) 353 m

Answer (3)

Question.Three sound waves of equal amplitudes have frequencies (n – 1), n, (n + 1). They superimpose to give beats.The number of beats produced per second will be 

(1) 1

(2) 4

(3) 3

(4) 2

Answer (4)

Question.When two tuning forks (fork 1 and fork 2) are sounded together, 4 beats per second are heard. Now some tape is attached on the prong of the fork 2. When the tuning forks are sounded again, 6 beats per second are heard. If the frequency of fork 1 is 200 Hz, then what was the original frequency of fork 2?

(1) 204 Hz

(2) 196 Hz

(3) 202 Hz

(4) 200 Hz

Answer (2)

Question.The frequency changes by 10% as a sound source approaches a stationary observer with constant speed V_s.What would be percentage change in the frequency as the source recedes the observer with same speed(V_s< V)?

(1) 10.5%

(2) 8.5%

(3) 4.5%

(4) 1.5%

Answer (2)

Question.The second overtone of an open organ pipe has the same frequency as the first overtone of a closed pipe L metre long. The length of the open pipe will be

(1) L

(2) 2L

(3)L/2

(4) 4L

Answer (2)

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

(1) 200 cm

(2) 66.7 cm

(3) 100 cm

(4) 150 cm

Answer (4)

Question.The number of possible natural oscillations of air column in a pipe closed at one end of length 85 cm whose frequencies lie below 1250 Hz are (velocity of sound = 340 ms^–1) 

(1) 4

(2) 5

(3) 7

(4) 6

Answer (4)

Question.A source of frequency v gives 5 beats/second when sounded with a source of frequency 200 Hz. The second harmonic of frequency 2v of source gives 10 beats/second when sounded with a source of frequency 420 Hz.The value of v is

(1) 205 Hz

(2) 195 Hz

(3) 200 Hz

(4) 210 Hz

Answer (1)

Question.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 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) 3500 Hz

(2) 4000 Hz

(3) 5000 Hz

(4) 3000 Hz

Answer (3)

Question.If we study the vibration of a pipe open at both ends, then the following statement is not true: 

(1) Odd harmonics of the fundamental frequency will be generated

(2) All harmonics of he fundamental frequency will be generated

(3) Pressure change will be maximum at both ends

(4) Open end will be antinode

Answer (3)

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 

(1) 246 Hz

(2) 240 Hz

(3) 260 Hz

(4) 254 Hz

Answer (4)

Question.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 meter and t in sec. The phase difference between them is 

(1) 0.57 radian

(2) 1.0 radian

(3) 1.25 radian

(4) 1.57 radian

Answer (2)

Question.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/hour 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 

(1) 1332 Hz

(2) 1372 Hz

(3) 1412 Hz

(4) 1454 Hz

Answer (3)

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

(1) Decreases by a factor 20

(2) Decreases by a factor 10

(3) Increases by a factor 20

(4) Increases by a factor 10

Answer (4)

Question.  Each of the two strings of length 51.6 cm and 49.1 cm are tensioned separately by 20 N force. Mass per unit length of both the strings is same and equal to 1 g/m. When both strings vibrate simultaneously the number of beats is 

(1) 7

(2) 8

(3) 3

(4) 5

Answer (1)

Question. Which one of the following statements is true?

(1) Both light and sound waves in air are transverse

(2) The sound waves in air are longitudinal while the light waves are transverse

(3) Both light and sound waves in air are longitudinal

(4) Both light and sound waves can travel in vacuum

Answer (2)

Question. Two waves of wavelengths 50 cm and 51 cm produced 12 beats per second. The velocity of sound is

(1) 340 m/s

(2) 331 m/s

(3) 306 m/s

(4) 360 m/s

Answer (3)

Question. The driver of a car travelling with speed 30 m/sec towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 m/s, the frequency of reflected sound as heard by driver is:

(1) 555.5 Hz

(2) 720 Hz

(3) 500 Hz

(4) 550 Hz

Answer (2)

Question. A wave in a string has an amplitude of 2 cm. The wave travels in the positive direction of x axis with a speed of 128 m/s and it is noted that 5 complete waves fit in 4 m length of the string. The equation describing the wave is 

(1) y = (0.02) m sin (15.7x – 2010t)

(2) y = (0.02) m sin (15.7x + 2010t)

(3) y = (0.02) m sin (7.85x – 1005t)

(4) y = (0.02) m sin (7.85x + 1005t)

Answer (3)

Question. Two points are located at a distance of 10 m and 15 m from the source of oscillation. The period of oscillation is 0.05 sec and the velocity of the wave is 300 m/sec. What is the phase difference between the oscillations of two points?

(1) π/6

(2) π/3

(3) 2π/3

(4) π

Answer (3)

Question. 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

(1) 9 : 4

(2) 2 : 3

(3) 3 : 2

(4) 4 : 9

Answer (1)

Question. 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 occurrence of 6 beats/s when both the wires oscillate together would be 

(1) 0.04

(2) 0.01

(3) 0.02

(4) 0.03

Answer (3)

Question. Two vibrating tuning forks produce progressive waves given by y₁= 4sin 500πt and y₂= 2sin 506πt. Number of beats produced per minute is

(1) 360

(2) 180

(3) 3

(4) 60

Answer (2)

Question. Which one of the following statements is true?

(1) The sound waves in air are longitudinal while the light waves are transverse

(2) Both light and sound waves in air are longitudinal

(3) Both light and sound waves can travel in vacuum

(4) Both light and sound waves in air are transverse

Answer (1)

Question. A wave of frequency 100 Hz travels along a string towards its fixed end. When this wave travels back, after reflection, a node is formed at a distance of 10 cm from the fixed end. The speed of the wave (incident and reflected) is

(1) 20 m/s

(2) 40 m/s

(3) 5 m/s

(4) 10 m/s

Answer (1)

Question. Two vibrating tuning forks produce progressive waves given by y₁ = 4sin 500 πt and y₂ = 2sin 506 πt. Number of beats produced per minute is

(1) 360

(2) 180

(3) 60

(4) 3

Answer (2)

Question.  A tuning fork of frequency 512 Hz makes 4 beats per second with the vibrating string of a piano. The beat frequency decreases to 2 beats per sec when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was

(1) 508 Hz

(2) 510 Hz

(3) 514 Hz

(4) 516 Hz

Answer (1)

Question. Two waves are represented by the equations
y₁= asin(ωt + kx + 0.57)m and
y₂= acos(ωt + kx) m, where x is in metre and t in second. The phase difference between them is

(1) 0.57 radian

(2) 1.0 radian

(3) 1.25 radian

(4) 1.57 radian

Answer (2)

Question. A standing wave having 3 nodes and 2 antinodes is formed between two atoms having a distance 1.21 Å between them. The wavelength of the standing wave is

(1) 6.05 Å

(2) 2.42 Å

(3) 1.21 Å

(4) 3.63 Å

Answer (3)