100 Important MCQs (Set-1) on Unit-8 Waves, Class 11 Physics (Unit-Wise Practice):
This post contains 100 carefully selected multiple-choice questions (MCQs) Set-2, from Unit-8: Waves of Class 11 Physics, designed strictly according to the FBISE syllabus. These MCQs include a well-balanced mix of conceptual and numerical problems, making them exam-ready, revision-friendly, and high-scoring.
Whether you are preparing for annual board examinations, chapter tests, or competitive entry tests, this comprehensive MCQ collection thoroughly covers all the fundamental principles of wave motion, sound, and oscillations, enabling students to master the chapter with confidence and accuracy.
This unit-wise MCQ set includes questions from:
- Description of wave motion using vibrations in ropes, springs, and ripple tanks
- Mechanical and electromagnetic waves and their propagation in different media
- Basic wave terminology including displacement, amplitude, period, wavelength, frequency, crest, trough, compression, and rarefaction
- Application of the wave equation in numerical problems
- Energy transfer through progressive waves
- Nature of sound waves and their propagation in different media
- Comparison between transverse and longitudinal waves
- Speed of sound in different media, Newton’s formula, and Laplace correction
- Factors affecting the speed of sound in air
- Principle of superposition of waves
- Interference of sound waves and formation of beats
- Formation of stationary waves and graphical explanation
- Nodes and antinodes and their physical significance
- Modes of vibration of stretched strings and vibrating air columns
- Fundamental frequency and harmonics in open and closed organ pipes
- Doppler effect for mechanical and electromagnetic waves
- Applications of Doppler effect in real life
- Principles and applications of ultrasound in medical diagnostics and technology
Each MCQ is provided with the correct answer and a clear, concise explanation, helping students:
- Strengthen conceptual understanding of wave phenomena
- Avoid common mistakes in numerical and conceptual questions
- Improve problem-solving skills related to waves, sound, and vibrations
- Achieve maximum marks in the MCQs section
This all-in-one MCQ collection is an essential tool for Class 11 students aiming to excel in physics exams and fully master the concepts of waves and sound.
Topic no. 1. Wave Motion & Basic Concepts
Wave motion is defined as:
a) Motion of particles only
b) Transfer of matter
c) Transfer of energy without transfer of matter
d) Random vibration
Correct Answer is option c. Transfer of energy without transfer of matter
Explanation: Waves carry energy but particles only oscillate.
2. Mechanical waves require:
a) Vacuum
b) Medium
c) Light
d) Electricity
Correct Answer is option b. Medium
Explanation: Mechanical waves cannot propagate without a medium.
3. Electromagnetic waves can travel in:
a) Solid only
b) Liquid only
c) Gas only
d) Vacuum
Correct Answer is option d. Vacuum
Explanation: EM waves do not need a medium.
4. Displacement in a wave is:
a) Distance travelled by wave
b) Distance between crests
c) Distance of particle from mean position
d) Height of wave
Correct Answer is option c. Distance of particle from mean position
Explanation: Displacement is instantaneous deviation from equilibrium.
5. Amplitude is:
a) Distance between two crests
b) Maximum displacement from mean position
c) Time for one vibration
d) Wave speed
Correct Answer is option b. Maximum displacement from mean position
Explanation: Amplitude indicates energy of wave.
6. Time period is:
a) Time for one oscillation
b) Distance between compressions
c) Wave velocity
d) Frequency
Correct Answer is option a. Time for one oscillation
Explanation: Period is time for one complete cycle.
7. Frequency is:
a) Distance per second
b) Number of oscillations per second
c) Time for one oscillation
d) Wave speed
Correct Answer is option b. Number of oscillations per second
Explanation: Frequency is measured in hertz.
8. Wavelength is:
a) Maximum displacement
b) Distance between two successive crests
c) Speed of wave
d) Time period
Correct Answer is option b. Distance between two successive crests
Explanation: It is spatial period of wave.
9. Crest is:
a) Lowest point of wave
b) Highest point of wave
c) Compression
d) Rarefaction
Correct Answer is option b. Highest point of wave
Explanation: Crest occurs in transverse waves.
10. Trough is:
a) Highest point
b) Lowest point
c) Compression
d) Rarefaction
Correct Answer is option b. Lowest point
Explanation: Opposite of crest.
Topic no. 2. Transverse & Longitudinal Waves
11. In transverse waves, particles vibrate:
a) Parallel to wave direction
b) Perpendicular to wave direction
c) Circularly
d) Randomly
Correct Answer is option b. Perpendicular to wave direction
Explanation: Example: waves on rope.
12. In longitudinal waves, particles vibrate:
a) Perpendicular to wave direction
b) Circularly
c) Parallel to wave direction
d) Randomly
Correct Answer is option c. Parallel to wave direction
Explanation: Sound waves are longitudinal.
13. Compression is a region of:
a) Low density
b) No particles
c) High density
d) Zero pressure
Correct Answer is option c. High density
Explanation: Particles are close together.
14. Rarefaction is a region of:
a) High density
b) Low density
c) No motion
d) High pressure
Correct Answer is option b. Low density
Explanation: Particles are far apart.
Topic no. 3. Wave Equation v = fλ
15. The wave equation is:
a) v = f/λ
b) v = fλ
c) v = λ/f
d) v = f²λ
Correct Answer is option b. v = fλ
Explanation: Fundamental wave relation.
16. If f = 50 Hz and λ = 2 m, wave speed is:
a) 25 m/s
b) 50 m/s
c) 100 m/s
d) 150 m/s
Correct Answer is option c. 100 m/s
Explanation: v = 50 × 2 = 100 m/s.
17. If v = 340 m/s and f = 170 Hz, λ is:
a) 1 m
b) 2 m
c) 3 m
d) 4 m
Correct Answer is option b. 2 m
Explanation: λ = v/f = 340/170 = 2 m.
18. If λ doubles and v constant, frequency becomes:
a) Double
b) Half
c) Same
d) Zero
Correct Answer is option b. Half
Explanation: f = v/λ, inversely proportional.
19. Energy in progressive wave is transferred by:
a) Mass transfer
b) Heat only
c) Particle vibration
d) Electric current
Correct Answer is option c. Particle vibration
Explanation: Energy propagates via oscillations.
Topic no. 4. Sound Waves & Speed of Sound
20. Sound waves are:
a) Electromagnetic
b) Mechanical longitudinal waves
c) Transverse waves
d) Light waves
Correct Answer is option b. Mechanical longitudinal waves
Explanation: Sound needs medium.
21. Speed of sound is maximum in:
a) Air
b) Water
c) Steel
d) Vacuum
Correct Answer is option c. Steel
Explanation: Sound travels fastest in solids.
22. Newton’s formula for speed of sound is:
a) v = √(γP/ρ)
b) v = √(P/ρ)
c) v = fλ
d) v = λ/T
Correct Answer is option b. v = √(P/ρ)
Explanation: Newton assumed isothermal process.
23. Laplace correction introduced:
a) Pressure change
b) Temperature correction
c) Adiabatic process factor γ
d) Density correction
Correct Answer is option c. Adiabatic process factor γ
Explanation: Corrected Newton’s formula.
24. Correct formula for speed of sound in air:
a) v = √(P/ρ)
b) v = √(γP/ρ)
c) v = fλ
d) v = λf²
Correct Answer is option b. √(γP/ρ)
Explanation: Laplace corrected formula.
25. Speed of sound depends on:
a) Frequency
b) Amplitude
c) Medium properties
d) Wave height
Correct Answer is option c. Medium properties
Explanation: Depends on elasticity and density.
Topic no. 5. Superposition & Interference
26. Principle of superposition states:
a) Waves destroy each other
b) Waves reflect
c) Resultant displacement is sum of individual displacements
d) Waves stop
Correct Answer is option c.
Explanation: Fundamental wave principle.
27. Interference occurs when:
a) Two waves meet
b) Only one wave exists
c) Medium absent
d) Waves stop
Correct Answer is option a. Two waves meet
Explanation: Superposition of coherent waves.
28. Constructive interference occurs when:
a) Waves are out of phase
b) Waves are in phase
c) Frequencies differ
d) Medium absent
Correct Answer is option b. In phase
Explanation: Amplitudes add.
29. Destructive interference occurs when:
a) Waves in phase
b) Waves perpendicular
c) Waves out of phase by π
d) Medium changes
Correct Answer is option c. Out of phase by π
Explanation: Amplitudes cancel.
30. Beats are produced by:
a) Coherent sources
b) Non-coherent sources with close frequencies
c) Same frequency waves
d) Reflected waves
Correct Answer is option b.
Explanation: Beats occur due to frequency difference.
Topic no. 6. Stationary Waves
31. Stationary waves are formed by:
a) Progressive waves
b) Reflection of waves
c) Electric current
d) Heat
Correct Answer is option b. Reflection of waves
Explanation: Superposition of incident and reflected waves.
32. A node is a point of:
a) Maximum displacement
b) Zero displacement
c) Compression
d) Rarefaction
Correct Answer is option b. Zero displacement
Explanation: Particle does not vibrate.
33. An antinode is a point of:
a) Zero displacement
b) Maximum displacement
c) Compression
d) Rarefaction
Correct Answer is option b. Maximum displacement
Explanation: Maximum vibration.
34. Distance between two successive nodes is:
a) λ
b) λ/2
c) λ/4
d) 2λ
Correct Answer is option b. λ/2
Explanation: Node spacing.
35. Distance between node and antinode is:
a) λ
b) λ/2
c) λ/4
d) 2λ
Correct Answer is option c. λ/4
Explanation: Quarter wavelength.
Topic no. 7. Vibrating Strings & Air Columns
36. Fundamental frequency of stretched string is:
a) v/2L
b) v/L
c) 2v/L
d) v/4L
Correct Answer is option a. v/2L
Explanation: First harmonic.
37. For nth harmonic of string:
a) f = nv/2L
b) f = v/2nL
c) f = v/nL
d) f = 2nv/L
Correct Answer is option a. nv/2L
Explanation: Harmonic formula.
38. Closed organ pipe fundamental frequency:
a) v/2L
b) v/4L
c) v/L
d) 2v/L
Correct Answer is option b. v/4L
Explanation: Closed pipe supports odd harmonics.
39. Open organ pipe fundamental frequency:
a) v/2L
b) v/4L
c) v/L
d) v/8L
Correct Answer is option a. v/2L
Explanation: Both ends antinodes.
40. Closed pipe supports:
a) All harmonics
b) Even harmonics only
c) Odd harmonics only
d) No harmonics
Correct Answer is option c. Odd harmonics only
Explanation: Node at closed end.
Topic no. 8. Doppler Effect
41. Doppler effect is:
a) Reflection
b) Refraction
c) Change in frequency due to motion
d) Interference
Correct Answer is option c.
Explanation: Relative motion causes frequency change.
42. When source approaches observer, frequency:
a) Decreases
b) Increases
c) Remains same
d) Becomes zero
Correct Answer is option b. Increases
Explanation: Wavefronts compress.
43. When source moves away, frequency:
a) Increases
b) Decreases
c) Constant
d) Infinite
Correct Answer is option b. Decreases
Explanation: Wavefronts spread.
44. Doppler effect applies to:
a) Sound only
b) Light only
c) Mechanical waves only
d) All waves including EM waves
Correct Answer is option d.
Explanation: Applies to all waves.
Topic no. 9. Ultrasound
45. Ultrasound frequency is:
a) <20 Hz
b) 20–20,000 Hz
c) >20,000 Hz
d) Zero
Correct Answer is option c. >20,000 Hz
Explanation: Beyond human hearing.
46. Ultrasound is used in:
a) Cooking
b) X-rays
c) Medical imaging
d) Radio communication
Correct Answer is option c. Medical imaging
Explanation: Used in sonography.
47. Ultrasound imaging works on:
a) Reflection of waves
b) Diffraction
c) Refraction
d) Polarization
Correct Answer is option a. Reflection of waves
Explanation: Echo technique.
NUMERICAL MCQs
48. If v=300 m/s and λ=3 m, f=?
a) 50 Hz
b) 100 Hz
c) 150 Hz
d) 200 Hz
Correct Answer is option b. 100 Hz
Explanation: f = v/λ = 300/3 = 100 Hz.
49. A wave has f=25 Hz and λ=4 m, v=?
a) 50 m/s
b) 75 m/s
c) 100 m/s
d) 200 m/s
Correct Answer is option c. 100 m/s
Explanation: v=fλ=25×4.
50. If frequency doubles, wavelength becomes:
a) Double
b) Half
c) Same
d) Zero
Correct Answer is option b. Half
Explanation: f inversely proportional to λ.
Numerical & Conceptual MCQs
51. A wave travels 600 m in 2 s. Its speed is:
a) 100 m/s
b) 200 m/s
c) 300 m/s
d) 400 m/s
Correct Answer is option c. 300 m/s
Explanation: v = distance/time = 600/2 = 300 m/s.
52. If wavelength is 0.5 m and speed is 250 m/s, frequency is:
a) 100 Hz
b) 250 Hz
c) 500 Hz
d) 1000 Hz
Correct Answer is option c. 500 Hz
Explanation: f = v/λ = 250/0.5 = 500 Hz.
53. A sound wave has frequency 500 Hz and speed 340 m/s. Wavelength is:
a) 0.34 m
b) 0.68 m
c) 1 m
d) 2 m
Correct Answer is option b. 0.68 m
Explanation: λ = v/f = 340/500.
54. The energy of a wave depends on:
a) Wavelength only
b) Frequency only
c) Amplitude
d) Speed
Correct Answer is option c. Amplitude
Explanation: Energy ∝ amplitude².
55. If amplitude becomes zero, wave energy becomes:
a) Maximum
b) Double
c) Zero
d) Infinite
Correct Answer is option c. Zero
Explanation: No vibration means no energy transfer.
Topic no. 10. Speed of Sound Factors
56. Speed of sound increases with:
a) Decrease in temperature
b) Increase in density only
c) Increase in temperature
d) Decrease in pressure
Correct Answer is option c. Increase in temperature
Explanation: Sound speed increases with temperature.
57. Speed of sound in a medium depends on:
a) Frequency
b) Amplitude
c) Elasticity and density
d) Loudness
Correct Answer is option c. Elasticity and density
Explanation: v = √(Elasticity/Density).
58. Sound travels slowest in:
a) Steel
b) Water
c) Air
d) Glass
Correct Answer is option c. Air
Explanation: Gas has lowest elasticity.
59. Newton’s assumption was that sound propagation is:
a) Adiabatic
b) Isothermal
c) Isobaric
d) Isochoric
Correct Answer is option b. Isothermal
Explanation: Newton assumed constant temperature.
60. Laplace corrected Newton by assuming process is:
a) Isothermal
b) Adiabatic
c) Isobaric
d) Isometric
Correct Answer is option b. Adiabatic
Explanation: Real sound propagation is adiabatic.
Topic no. 11. Interference & Beats
61. Interference pattern depends on:
a) Medium only
b) Frequency difference
c) Wave speed
d) Temperature
Correct Answer is option b. Frequency difference
Explanation: Phase relation depends on frequency.
62. For constructive interference, path difference must be:
a) λ/2
b) λ
c) λ/4
d) 3λ/2
Correct Answer is option b. λ
Explanation: Integral multiples of λ.
63. For destructive interference, path difference must be:
a) λ
b) 2λ
c) λ/2
d) 3λ
Correct Answer is option c. λ/2
Explanation: Odd multiples of λ/2.
64. Beats frequency equals:
a) f1 + f2
b) f1 – f2
c) f1 × f2
d) f1/f2
Correct Answer is option b. |f1 – f2|
Explanation: Beat frequency is difference of frequencies.
65. If f1=256 Hz and f2=260 Hz, beats per second are:
a) 2
b) 4
c) 6
d) 8
Correct Answer is option b. 4
Explanation: |260 − 256| = 4 beats/s.
Topic no. 12. Stationary Waves
66. Stationary waves do not transfer:
a) Energy
b) Mass
c) Displacement
d) Frequency
Correct Answer is option a. Energy
Explanation: No net energy transfer.
67. Maximum strain occurs at:
a) Node
b) Antinode
c) Midpoint
d) Everywhere
Correct Answer is option a. Node
Explanation: Adjacent particles move in opposite directions.
68. Distance between two successive antinodes is:
a) λ
b) λ/2
c) λ/4
d) 2λ
Correct Answer is option b. λ/2
Explanation: Same as nodes.
Topic no. 13. Vibrating Strings
69. Frequency of string depends on:
a) Length
b) Tension
c) Mass per unit length
d) All of these
Correct Answer is option d. All of these
Explanation: f = (1/2L)√(T/μ).
70. If length of string doubles, fundamental frequency becomes:
a) Double
b) Half
c) Same
d) Zero
Correct Answer is option b. Half
Explanation: f ∝ 1/L.
71. If tension becomes four times, frequency becomes:
a) Double
b) Half
c) Same
d) Quadruple
Correct Answer is option a. Double
Explanation: f ∝ √T.
Topic no. 14. Air Columns
72. In open organ pipe, both ends are:
a) Nodes
b) Antinodes
c) One node one antinode
d) Closed
Correct Answer is option b. Antinodes
Explanation: Air vibrates freely.
73. In closed pipe, closed end is:
a) Node
b) Antinode
c) Crest
d) Trough
Correct Answer is option a. Node
Explanation: No displacement at closed end.
74. In closed pipe, first overtone frequency is:
a) f
b) 2f
c) 3f
d) 4f
Correct Answer is option c. 3f
Explanation: Only odd harmonics exist.
Topic no. 15. Doppler Effect
75. Observer approaches stationary source, perceived frequency:
a) Decreases
b) Increases
c) Same
d) Zero
Correct Answer is option b. Increases
Explanation: Relative motion compresses waves.
76. Source moves away, observer stationary. Frequency:
a) Increases
b) Decreases
c) Same
d) Infinite
Correct Answer is option b. Decreases
Explanation: Wavefronts spread.
77. Doppler effect for light is called:
a) Echo
b) Redshift
c) Interference
d) Beats
Correct Answer is option b. Redshift
Explanation: Frequency shift in EM waves.
Topic no. 16. Ultrasound & Applications
78. Medical ultrasound frequency range is typically:
a) 20–200 Hz
b) 20–20,000 Hz
c) Above 20 kHz
d) Below 20 Hz
Correct Answer is option c. Above 20 kHz
Explanation: High-frequency waves.
79. Ultrasound is used to detect:
a) Radio signals
b) Earthquakes
c) Internal body structures
d) Light waves
Correct Answer is option c. Internal body structures
Explanation: Sonography imaging.
80. SONAR uses:
a) Infrared
b) Radio waves
c) Ultrasound
d) X-rays
Correct Answer is option c. Ultrasound
Explanation: Underwater detection.
More Numericals MCQs
81. If v=340 m/s and f=680 Hz, λ=?
a) 0.25 m
b) 0.5 m
c) 1 m
d) 2 m
Correct Answer is option b. 0.5 m
Explanation: λ = v/f.
82. A wave has λ=5 m and f=2 Hz. v=?
a) 5 m/s
b) 10 m/s
c) 15 m/s
d) 20 m/s
Correct Answer is option b. 10 m/s
Explanation: v=fλ.
83. If frequency becomes 3 times, wavelength becomes:
a) 3 times
b) 1/3
c) Same
d) Zero
Correct Answer is option b. 1/3
Explanation: Inverse relation.
Conceptual MCQs
84. Sound cannot travel in:
a) Solid
b) Liquid
c) Gas
d) Vacuum
Correct Answer is option d. Vacuum
Explanation: Needs medium.
85. Light is a:
a) Mechanical wave
b) Longitudinal wave
c) Electromagnetic transverse wave
d) Sound wave
Correct Answer is option c.
Explanation: Light does not need medium.
86. Reflection of sound produces:
a) Beats
b) Echo
c) Interference
d) Refraction
Correct Answer is option b. Echo
Explanation: Reflection phenomenon.
87. Echo is heard when time delay is more than:
a) 0.01 s
b) 0.1 s
c) 0.5 s
d) 1 s
Correct Answer is option b. 0.1 s
Explanation: Persistence of hearing.
Stationary Wave Numericals MCQs
88. If L=1 m and v=200 m/s, fundamental frequency of string:
a) 50 Hz
b) 100 Hz
c) 200 Hz
d) 400 Hz
Correct Answer is option b. 100 Hz
Explanation: f=v/2L.
89. Second harmonic frequency is:
a) f
b) 2f
c) 3f
d) 4f
Correct Answer is option b. 2f
Explanation: Harmonic relation.
90. Third harmonic wavelength for string length L is:
a) 2L
b) L
c) 2L/3
d) L/3
Correct Answer is option c. 2L/3
Explanation: λn = 2L/n.
Doppler Conceptual MCQs
91. Siren pitch rises when ambulance approaches because:
a) Amplitude increases
b) Frequency increases
c) Wavelength increases
d) Speed changes
Correct Answer is option b. Frequency increases
Explanation: Doppler effect.
92. Doppler effect is used in:
a) Radar
b) MRI
c) Telescope only
d) Battery
Correct Answer is option a. Radar
Explanation: Velocity measurement.
Mixed MCQs
93. Progressive waves transfer:
a) Mass
b) Energy
c) Matter
d) Particles
Correct Answer is option b. Energy
Explanation: Energy propagation.
94. The SI unit of frequency is:
a) m
b) s
c) Hz
d) J
Correct Answer is option c. Hz
Explanation: Hertz.
95. Phase difference of π means:
a) Constructive interference
b) Destructive interference
c) Same phase
d) No interference
Correct Answer is option b. Destructive interference
Explanation: Waves cancel.
96. If beat frequency is zero, waves are:
a) Different
b) Coherent
c) Same frequency
d) Opposite phase
Correct Answer is option c. Same frequency
Explanation: No beats.
97. In stationary waves, particles:
a) Move with wave
b) Remain at rest
c) Vibrate about fixed positions
d) Travel long distances
Correct Answer is option c. Vibrate about fixed positions
Explanation: No net motion.
98. Ultrasound cannot travel through:
a) Solid
b) Liquid
c) Gas
d) Vacuum
Correct Answer is option d. Vacuum
Explanation: Needs medium.
99. Wavelength is inversely proportional to:
a) Speed
b) Frequency
c) Amplitude
d) Time
Correct Answer is option b. Frequency
Explanation: λ = v/f.
100. Loudness of sound depends on:
a) Frequency
b) Wavelength
c) Amplitude
d) Speed
Correct Answer is option c. Amplitude
Explanation: Greater amplitude means louder sound.
 on Waves | Class 11 Physics | Unit 8){kind=link}
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