JEE Physics Waves MCQs Set B

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?

• a) 15 cm
• b) 25 cm
• c) 30 cm
• d) 5 cm

Answer: 15 cm

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

• a) 2 N
• b) 4 N
• c) 8 N
• d) 16 N

Answer: 2 N

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

• a)

  

• b)

  

• c) 1.5 cm
• d) 2 cm

Answer:

Question: A uniform string of fundamental frequency of vibration f is divided into two segments by means of a bridge. If f₁ and f₂ are fundamental frequencies of these segments then

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Two sound waves of intensity 2 W/m² and 3 W/m² meet at a point to produce a resultant intensity 5 W/m². The phase difference between two waves is

• a)

  

• b)

  

• c) Zero
• d)

  

Answer:

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

• a) Interference
• b) Stationary waves
• c) None of these
• d) Beats

Answer: Interference

Question: The string of a violin emits a note of 205 Hz at its correct tension. The string is tightened slightly and then it produces six beats in two seconds with a tuning fork of frequency 205 Hz. The frequency of the note emitted by the taut string is

• a) 208 Hz
• b) 202 Hz
• c) 199 Hz
• d) 211 Hz

Answer: 208 Hz

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?

• a) 196 Hz
• b) 204 Hz
• c) 202 Hz
• d) 200 Hz

Answer: 196 Hz

Question:

• a) 5000 Hz
• b) 3000 Hz
• c) 4000 Hz
• d) 3500 Hz

Answer: 5000 Hz

Question:

• a) 205 Hz
• b) 195 Hz
• c) 200 Hz
• d) 210 Hz

Answer: 205 Hz

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

• a) 15 m
• b) 25 m
• c) 9 m
• d)

  

Answer:  15 m

Question:

• a) 8.5%
• b) 4.5%
• c) .5%
• d) 10.5%

Answer: 8.5%

Question:  A train blowing its whistle moves with constant speed on a straight track towards observer and then crosses him. If the ratio of difference between the actual and apparent frequencies be 3 : 2 in the two cases, then the speed of train is [v is speed of sound]

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 1.0 radian
• b) 1.57 radian
• c) 0.57 radian
• d) 1.25 radian

Answer: 1.0 radian

Question: A hospital uses an ultrasonic scanner to locate tumours in a tissue. The operating frequency of the scanner is 4.2 MHz. The speed of sound in a tissue is 1.7 km/s. The wavelength of sound in the tissue is close to

• a) 4 × 10^–4 m
• b) 4 × 10^–3 m
• c) 8 × 10^–3 m
• d) 8 × 10^–4 m

Answer: 4 × 10^–4 m

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) Increases by a factor 10
• b) Decreases by a factor 10
• c) Decreases by a factor 20
• d) Increases by a factor 20

Answer: Increases by a factor 10

Question:

• a)

  

• b)

  

• c) –ve x direction with frequency 1 Hz
• d)

  

Answer:

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 s and the velocity of the wave is 300 m/s. What is the phase difference between the oscillations of two points?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 4 m/s
• b) 2 m/s
• c) 8 m/s
• d) 12 m/s

Answer: 4 m/s

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

• a) kA
• b)

  

• c)

  

• d)

  

Answer: kA

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

• a)

  

• b)

  

• c)

  

• d) Zero

Answer:

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

• a) 720 Hz
• b) 555.5 Hz
• c) 550 Hz
• d) 500 Hz

Answer: 720 Hz

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

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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

• a) 0.64 I
• b) 0.4 I
• c) 0.8 I
• d) 0.36 I

Answer: 0.64 I

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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

• a) 10⁴ m/s
• b) Not derivable
• c) 1 m/s
• d) 10² m/s

Answer: 10⁴ m/s

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?

• a) 60 cm and 90 cm
• b) 30 cm and 60 cm
• c) 30 cm and 90 cm
• d) 40 cm and 80 cm

Answer: 60 cm and 90 cm

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

• a) 5 Hz
• b) 10 Hz
• c) 2 Hz
• d) 4 Hz

Answer: 5 Hz

Question: If the tension and diameter of a sonometer wire of fundamental frequency n is doubled and density is halved then its fundamental frequency will become

• a) n
• b)

  

• c)

  

• d)

  

Answer: n

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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

• a) None of these
• b)

  

• c)

  

• d)

  

Answer: None of these

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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

• a) 150, 450
• b) 400, 800
• c) 250, 400
• d) 75, 150

Answer: 150, 450

Question: A second harmonic has to be generated in a string of length l stretched between two rigid supports. The points where the string has to be plucked and touched are respectively

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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

• a) Different speeds at same instant
• b) Same speed at same instant
• c) Different speeds at different instants
• d) Same speed at different instants

Answer: Different speeds at same instant

Question:

• a) 1 : 16
• b) 1 : 8
• c) 1 : 4
• d) 1 : 2

Answer: 1 : 16

Question:  Two sound waves having a phase difference of 60° have path difference of

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 1.07 radian
• b) 2.07 radian
• c) 0.5 radian
• d) 1.5 radian

Answer:  1.07 radian

Question:

• a) 8 m/s
• b)

  

• c)

  

• d)

  

Answer: 8 m/s

Question: A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distances 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) 4 : 9
• c) 2 : 3
• d) 3 : 2

Answer: 9 : 4

Question: The time of reverberation of a room A is one second. What will be the time (in second) of reverberation of a room, having all the dimensions double of those of room A?

• a) 2
• b) 2
• c) 4
• d)

  

Answer: 2

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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 per second when both the wires oscillate together would be

• a) 0.02
• b) 0.03
• c) 0.01
• d) 0.04

Answer: 0.02

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

• a) 20 m/s
• b) 40 m/s
• c) 5 m/s
• d) 10 m/s

Answer: 20 m/s

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

• a) 1.21 Å
• b) 3.63 Å
• c) 2.42 Å
• d) 6.05 Å

Answer: 1.21 Å

Question: 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 m/s and it is noted that 5 complete waves fit in 4 m length of the string. The equation describing the wave is

• a) y = (0.02) m sin(7.85x – 1005t)
• b) y = (0.02) m sin(7.85x + 1005t)
• c) y = (0.02) m sin(15.7x + 2010t)
• d) y = (0.02) m sin(15.7x – 2010t)

Answer: y = (0.02) m sin(7.85x – 1005t)

Question:

• a) 4 beats per second with intensity ratio 81 : 1 between waxing and waning
• b) 8 beats per second with intensity ratio 81 : 1 between waxing and waning
• c) 4 beats per second with intensity ratio 25 : 16 between waxing and waning
• d) 8 beats per second with intensity ratio 25 : 16 between waxing and waning

Answer: 4 beats per second with intensity ratio 81 : 1 between waxing and waning

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

• a) 306 m/s
• b) 360 m/s
• c) 331 m/s
• d) 340 m/s

Answer: 306 m/s

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 180
• b) 60
• c) 3
• d) 360

Answer: 180

Question: Two sound waves with wavelengths 5.0 m and 5.5 m respectively, each propagate in a gas with velocity 330 m/s. We expect the following number of beats per second

• a) 6
• b) 12
• c) Zero
• d) 1

Answer: 6

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 the strings vibrate simultaneously the number of beats is

• a) 7
• b) 8
• c) 5
• d) 3

Answer: 7

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 second when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was

• a) 508 Hz
• b) 510 Hz
• c) 514 Hz
• d) 516 Hz

Answer: 508 Hz

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 374 Hz
• b) 394 Hz
• c) 333 Hz
• d) 385 Hz

Answer: 374 Hz

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  Which one of the following statements is true?

• a) The sound waves in air are longitudinal while the light waves are transverse
• b) Both light and sound waves in air are longitudinal
• c) Both light and sound waves can travel in vacuum
• d) Both light and sound waves in air are transverse

Answer: The sound waves in air are longitudinal while the light waves are transverse