100 Important Basic MCQs (Level -1) on Waves Motion, Physics (Unit-Wise MCQs Practice):

👉Physics MCQs Hub – Unit wise Physics MCQs Practice (Main-Page)👈

Whether you are preparing for board examinations, chapter tests, college assessments, or competitive entrance exams (MDCAT, ECAT, NUST, PIEAS, GIKI, UET, FAST, and other engineering or medical admission tests), this comprehensive Wave Motion MCQ Collection is designed to help you master every important concept of wave motion and sound. The questions are arranged progressively—from basic concepts to advanced numerical problems and higher-order thinking—ensuring complete and systematic preparation for every type of examination.

This chapter-wise MCQ collection includes:

100 Basic MCQs Level-1 (1–100) – Covering the fundamental concepts of wave motion, types of waves, wave characteristics, sound waves, wave propagation, reflection, refraction, diffraction, interference, standing waves, Doppler Effect, ultrasound, and SONAR.
100 Advanced & Numerical MCQs (101–200) – Focusing on wave equations, speed of sound calculations, beats, harmonics, organ pipes, vibrating strings, Doppler Effect numericals, ultrasound, SONAR, echo calculations, and practical problem-solving.
50 Higher-Order Thinking Skills (HOTS) MCQs (201–250) – Designed to strengthen analytical reasoning, conceptual understanding, assertion–reason questions, experimental analysis, real-life applications, and multi-concept problem-solving skills.
50 Challenging MCQs Quiz with Answers – A carefully selected mix of conceptual, numerical, and HOTS questions designed for quick revision, self-assessment, and complete exam preparation.

This MCQ collection covers:

Fundamentals of Wave Motion
Mechanical and Electromagnetic Waves
Transverse and Longitudinal Waves
Wave Characteristics (Amplitude, Wavelength, Frequency, Time Period, Wave Speed)
Wave Equation $(v=f\lambda)$
Propagation of Sound Waves
Speed of Sound in Solids, Liquids, and Gases
Effect of Temperature on the Speed of Sound
Newton's Formula and Laplace Correction
Reflection, Refraction, and Diffraction of Waves
Principle of Superposition
Interference of Waves
Constructive and Destructive Interference
Beats and Beat Frequency
Standing Waves
Nodes and Antinodes
Vibrating Strings
Harmonics and Overtones
Open and Closed Organ Pipes
Doppler Effect
Ultrasound and Piezoelectric Effect
Medical Applications of Ultrasound
SONAR and Echo Sounding
Echolocation in Bats and Dolphins
Real-Life Applications of Wave Motion

Every MCQ includes the correct answer along with a clear, concept-based explanation to strengthen understanding, improve problem-solving skills, and reinforce important physics concepts.

This question bank helps students to:

Build a strong conceptual foundation in Wave Motion
Master wave properties and sound propagation
Improve numerical and analytical problem-solving skills
Understand interference, standing waves, harmonics, and resonance
Strengthen concepts of the Doppler Effect, ultrasound, and SONAR
Avoid common examination mistakes
Increase speed, accuracy, and confidence in objective-type questions
Prepare effectively for both board examinations and competitive entrance tests

With 250 carefully selected MCQs arranged into 100 Basic, 100 Advanced & Numerical, and 50 Higher-Order Thinking (HOTS) questions, along with a Top 50 Challenging MCQs Quiz, this all-in-one Wave Motion MCQ Bank provides complete chapter preparation. It is an excellent study resource for strengthening concepts, improving exam performance, and achieving success in both board examinations and competitive physics entrance tests.

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Waves Motion MCQs (Level 1) – 100 Basic MCQs with Answers (MCQs 1–100)

MCQs 1–25 – Fundamentals of Wave Motion

MCQ No. 1

Wave motion is the transfer of:

a) Matter from one place to another

b) Energy without transfer of matter

c) Mass and energy together

d) Particles only

Correct Answer: b) Energy without transfer of matter

Explanation: Wave motion transfers energy from one place to another while the particles of the medium only vibrate about their mean positions.

MCQ No. 2

The particles of a medium in a wave generally:

a) Move with the wave

b) Travel long distances

c) Vibrate about their mean positions

d) Remain stationary

Correct Answer: c) Vibrate about their mean positions

Explanation: The medium does not travel with the wave; only energy propagates through it.

MCQ No. 3

Mechanical waves require:

a) Vacuum

b) Material medium

c) Electric field

d) Magnetic field

Correct Answer: b) Material medium

Explanation: Mechanical waves cannot travel without a material medium.

MCQ No. 4

Which one of the following is an electromagnetic wave?

a) Sound wave

b) Water wave

c) Light wave

d) Seismic wave

Correct Answer: c) Light wave

Explanation: Light is an electromagnetic wave and can travel through a vacuum.

MCQ No. 5

Which wave can travel through vacuum?

a) Sound wave

b) Water wave

c) Light wave

d) Seismic wave

Correct Answer: c) Light wave

Explanation: Electromagnetic waves do not require a material medium.

MCQ No. 6

The SI unit of frequency is:

a) Meter

b) Second

c) Hertz

d) Joule

Correct Answer: c) Hertz

Explanation: Frequency is measured in hertz (Hz), where 1 Hz equals one vibration per second.

MCQ No. 7

The time taken to complete one vibration is called:

a) Frequency

b) Wavelength

c) Time period

d) Amplitude

Correct Answer: c) Time period

Explanation: Time period is the duration of one complete oscillation.

MCQ No. 8

Frequency is equal to:

a) Number of oscillations per second

b) Distance travelled in one second

c) Height of a wave

d) Speed of wave

Correct Answer: a) Number of oscillations per second

Explanation: Frequency indicates how many complete vibrations occur each second.

MCQ No. 9

Amplitude is:

a) Distance between two crests

b) Maximum displacement from the mean position

c) Time for one vibration

d) Distance travelled by a wave

Correct Answer: b) Maximum displacement from the mean position

Explanation: Greater amplitude means more energy is carried by the wave.

MCQ No. 10

The distance between two successive crests is called:

a) Time period

b) Frequency

c) Wavelength

d) Amplitude

Correct Answer: c) Wavelength

Explanation: Wavelength is the shortest distance between two points in the same phase.

MCQ No. 11

The highest point of a transverse wave is called:

a) Trough

b) Crest

c) Compression

d) Rarefaction

Correct Answer: b) Crest

Explanation: Crest is the point of maximum positive displacement.

MCQ No. 12

The lowest point of a transverse wave is called:

a) Crest

b) Compression

c) Trough

d) Rarefaction

Correct Answer: c) Trough

Explanation: Trough is the point of maximum negative displacement.

MCQ No. 13

In longitudinal waves, regions of high pressure are called:

a) Crests

b) Troughs

c) Compressions

d) Nodes

Correct Answer: c) Compressions

Explanation: During compression, particles are crowded closer together.

MCQ No. 14

Regions of low pressure in a longitudinal wave are called:

a) Crests

b) Rarefactions

c) Nodes

d) Antinodes

Correct Answer: b) Rarefactions

Explanation: Rarefactions are regions where particles are farther apart.

MCQ No. 15

The displacement of a vibrating particle is measured from its:

a) Crest

b) Trough

c) Mean position

d) Wavelength

Correct Answer: c) Mean position

Explanation: Displacement is the distance of a particle from its equilibrium position.

MCQ No. 16

A progressive wave transfers:

a) Matter only

b) Energy only

c) Both matter and energy

d) Neither matter nor energy

Correct Answer: b) Energy only

Explanation: Progressive waves carry energy without transporting matter.

MCQ No. 17

The relationship between wave speed, frequency, and wavelength is:

a) $v=\frac{f}{\lambda}$

b) $v=f\lambda$

c) $v=\frac{\lambda}{f}$

d) $v=f^2\lambda$

Correct Answer: b) $v=f\lambda$

Explanation: This is the fundamental equation of wave motion.

MCQ No. 18

If frequency increases while wave speed remains constant, wavelength:

a) Increases

b) Decreases

c) Remains constant

d) Becomes zero

Correct Answer: b) Decreases

Explanation: Since $v=f\lambda$ , wavelength is inversely proportional to frequency.

MCQ No. 19

If wavelength doubles while wave speed remains constant, frequency:

a) Doubles

b) Becomes half

c) Remains unchanged

d) Becomes four times

Correct Answer: b) Becomes half

Explanation: Frequency and wavelength are inversely related.

MCQ No. 20

A wave has a frequency of 40 Hz and wavelength of 5 m. Its speed is:

a) 100 m/s

b) 150 m/s

c) 200 m/s

d) 250 m/s

Correct Answer: c) 200 m/s

Explanation: $v=f\lambda=40\times5=200\ \text{m/s}$

MCQ No. 21

A wave travels with a speed of 300 m/s and has a frequency of 100 Hz. Its wavelength is:

a) 1 m

b) 2 m

c) 3 m

d) 4 m

Correct Answer: c) 3 m

Explanation: $\lambda=\frac{v}{f}=\frac{300}{100}=3\ \text{m}$

MCQ No. 22

If the frequency of a wave is 25 Hz, its time period is:

a) 0.02 s

b) 0.04 s

c) 0.25 s

d) 4 s

Correct Answer: b) 0.04 s

Explanation: $T=\frac{1}{f}=\frac{1}{25}=0.04\ \text{s}$

MCQ No. 23

The wave equation is applicable to:

a) Mechanical waves only

b) Electromagnetic waves only

c) All types of waves

d) Sound waves only

Correct Answer: c) All types of waves

Explanation: The equation $v = f λ is valid for all waves.$

MCQ No. 24

The energy carried by a wave mainly depends upon its:

a) Frequency only

b) Amplitude

c) Wavelength only

d) Speed

Correct Answer: b) Amplitude

Explanation: Wave energy is proportional to the square of its amplitude $(E\propto A^2)$ .

MCQ No. 25

Which of the following statements is correct?

a) Waves transport matter from one place to another.

b) Mechanical waves can travel through vacuum.

c) Electromagnetic waves can travel without a material medium.

d) Sound waves are electromagnetic waves.

Correct Answer: c) Electromagnetic waves can travel without a material medium.

Explanation: Electromagnetic waves propagate through vacuum, whereas mechanical waves require a material medium.

MCQs 26–50 – Transverse & Longitudinal Waves, Sound & Speed of Sound

MCQ No. 26

In a transverse wave, the particles of the medium vibrate:

a) Parallel to the direction of wave propagation

b) Perpendicular to the direction of wave propagation

c) Along a circular path

d) Randomly

Correct Answer: b) Perpendicular to the direction of wave propagation

Explanation: In transverse waves, particles oscillate at right angles to the direction in which the wave travels.

MCQ No. 27

An example of a transverse mechanical wave is:

a) Sound in air

b) Compression wave

c) Wave on a stretched string

d) Ultrasonic wave in air

Correct Answer: c) Wave on a stretched string

Explanation: Waves produced on a stretched rope or string are transverse mechanical waves.

MCQ No. 28

In a longitudinal wave, particles vibrate:

a) Perpendicular to wave propagation

b) Parallel to wave propagation

c) Vertically

d) Randomly

Correct Answer: b) Parallel to wave propagation

Explanation: Longitudinal waves consist of compressions and rarefactions along the direction of travel.

MCQ No. 29

Which of the following is a longitudinal wave?

a) Light wave

b) Radio wave

c) Sound wave in air

d) Water surface wave

Correct Answer: c) Sound wave in air

Explanation: Sound propagates through air as a longitudinal mechanical wave.

MCQ No. 30

A crest and a trough are associated with:

a) Longitudinal waves

b) Transverse waves

c) Sound waves only

d) Pressure waves only

Correct Answer: b) Transverse waves

Explanation: Crests and troughs are characteristic features of transverse waves.

MCQ No. 31

Compressions and rarefactions are produced in:

a) Electromagnetic waves

b) Transverse waves

c) Longitudinal waves

d) Standing waves only

Correct Answer: c) Longitudinal waves

Explanation: These regions are formed due to the periodic motion of particles in longitudinal waves.

MCQ No. 32

Sound waves are classified as:

a) Electromagnetic transverse waves

b) Mechanical longitudinal waves

c) Mechanical transverse waves

d) Electromagnetic longitudinal waves

Correct Answer: b) Mechanical longitudinal waves

Explanation: Sound requires a material medium and propagates through compressions and rarefactions.

MCQ No. 33

The speed of sound is greatest in:

a) Air

b) Water

c) Steel

d) Vacuum

Correct Answer: c) Steel

Explanation: Solids possess high elasticity, allowing sound to travel much faster than in liquids or gases.

MCQ No. 34

Sound cannot travel through:

a) Air

b) Water

c) Steel

d) Vacuum

Correct Answer: d) Vacuum

Explanation: A material medium is essential for the propagation of sound.

MCQ No. 35

The speed of sound mainly depends upon:

a) Elasticity and density of the medium

b) Loudness of sound

c) Frequency of sound

d) Amplitude of sound

Correct Answer: a) Elasticity and density of the medium

Explanation: Greater elasticity generally increases the speed, while greater density tends to reduce it.

MCQ No. 36

Newton assumed that the propagation of sound in air is:

a) Adiabatic

b) Isothermal

c) Isobaric

d) Isochoric

Correct Answer: b) Isothermal

Explanation: Newton assumed constant temperature during sound propagation, which underestimated the speed of sound.

MCQ No. 37

Laplace corrected Newton's formula by assuming the process is:

a) Isothermal

b) Adiabatic

c) Isobaric

d) Isochoric

Correct Answer: b) Adiabatic

Explanation: Sound propagates too rapidly for heat exchange; therefore, the process is adiabatic.

MCQ No. 38

Newton's formula for the speed of sound in air is:

a) $v=\sqrt{\frac{\gamma P}{\rho}}$

b) $v=f\lambda$

c) $v=\sqrt{\frac{P}{\rho}}$

d) $v=\frac{\lambda}{T}$

Correct Answer: c) $v=\sqrt{\frac{P}{\rho}}$

Explanation: This is Newton's original formula based on the isothermal assumption.

MCQ No. 39

Laplace's corrected formula for the speed of sound is:

a) $v=\sqrt{\frac{P}{\rho}}$

b) $v=\sqrt{\frac{\gamma P}{\rho}}$

c) $v=f\lambda$

d) $v=\frac{\lambda}{T}$

Correct Answer: b) $v=\sqrt{\frac{\gamma P}{\rho}}$

Explanation: Laplace introduced the ratio of specific heats (γ), bringing theory into agreement with experiment.

MCQ No. 40

The symbol γ in Laplace's formula represents:

a) Density

b) Pressure

c) Ratio of specific heats

d) Frequency

Correct Answer: c) Ratio of specific heats

Explanation: γ is the ratio of the specific heat at constant pressure to that at constant volume.

MCQ No. 41

The speed of sound in air increases with:

a) Increase in temperature

b) Decrease in temperature

c) Increase in humidity only

d) Increase in loudness

Correct Answer: a) Increase in temperature

Explanation: As temperature rises, gas molecules move faster, increasing the speed of sound.

MCQ No. 42

Approximately, the speed of sound in air increases by:

a) 0.16 m/s per °C

b) 0.61 m/s per °C

c) 1.61 m/s per °C

d) 2.61 m/s per °C

Correct Answer: b) 0.61 m/s per °C

Explanation: This is the standard approximation used in school and board examinations.

MCQ No. 43

At constant temperature, increasing the pressure of a gas has what effect on the speed of sound?

a) It increases.

b) It decreases.

c) It remains unchanged.

d) It becomes zero.

Correct Answer: c) It remains unchanged.

Explanation: Pressure and density increase proportionally, so their ratio remains nearly constant.

MCQ No. 44

Which property of solids is mainly responsible for the high speed of sound?

a) Colour

b) Elasticity

c) Shape

d) Mass

Correct Answer: b) Elasticity

Explanation: High elasticity allows sound disturbances to travel rapidly through solids.

MCQ No. 45

Among the following, the speed of sound is minimum in:

a) Steel

b) Water

c) Air

d) Glass

Correct Answer: c) Air

Explanation: Gases have much lower elasticity than solids and liquids.

MCQ No. 46

The speed of sound in gases depends primarily on:

a) Temperature and nature of the gas

b) Loudness only

c) Frequency only

d) Wavelength only

Correct Answer: a) Temperature and nature of the gas

Explanation: The molecular properties and temperature of the gas determine the speed of sound.

MCQ No. 47

Which statement about sound waves is correct?

a) They transfer matter from one place to another.

b) They are electromagnetic waves.

c) They require a material medium for propagation.

d) They travel fastest in a vacuum.

Correct Answer: c) They require a material medium for propagation.

Explanation: Sound is a mechanical wave and cannot propagate in a vacuum.

MCQ No. 48

The main reason Newton's formula underestimated the speed of sound was:

a) Wrong value of density

b) Wrong value of pressure

c) Incorrect isothermal assumption

d) Incorrect wavelength

Correct Answer: c) Incorrect isothermal assumption

Explanation: The propagation of sound is adiabatic rather than isothermal.

MCQ No. 49

Which scientist modified Newton's theory of sound by introducing the adiabatic correction?

a) Maxwell

b) Einstein

c) Laplace

d) Faraday

Correct Answer: c) Laplace

Explanation: Laplace's correction accurately explained the measured speed of sound.

MCQ No. 50

Which statement correctly compares sound and light?

a) Both require a material medium.

b) Both are longitudinal waves.

c) Sound requires a medium, whereas light can travel through a vacuum.

d) Light travels slower than sound in air.

Correct Answer: c) Sound requires a medium, whereas light can travel through a vacuum.

Explanation: Sound is a mechanical wave, while light is an electromagnetic wave capable of propagating through empty space.

MCQs 51–75 – Superposition, Interference, Beats & Standing Waves

MCQ No. 51

The principle of superposition states that when two or more waves overlap, the resultant displacement is:

a) The product of their displacements

b) The difference of their amplitudes

c) The algebraic sum of their individual displacements

d) Always zero

Correct Answer: c) The algebraic sum of their individual displacements

Explanation: According to the principle of superposition, the resultant displacement at any point is the algebraic sum of the individual displacements of all overlapping waves.

MCQ No. 52

Interference is a phenomenon that occurs due to:

a) Reflection of waves

b) Refraction of waves

c) Superposition of two or more waves

d) Diffraction of waves

Correct Answer: c) Superposition of two or more waves

Explanation: Interference results from the superposition of waves traveling through the same medium.

MCQ No. 53

Two sources producing waves of the same frequency with a constant phase difference are called:

a) Independent sources

b) Coherent sources

c) Random sources

d) Stationary sources

Correct Answer: b) Coherent sources

Explanation: Coherent sources maintain a constant phase difference and produce stable interference patterns.

MCQ No. 54

Constructive interference occurs when two waves meet:

a) In opposite phase

b) In the same phase

c) At right angles

d) With different frequencies

Correct Answer: b) In the same phase

Explanation: In-phase waves reinforce each other, producing a larger resultant amplitude.

MCQ No. 55

During constructive interference, the resultant amplitude is:

a) Zero

b) Less than either wave

c) Greater than either individual wave

d) Always unchanged

Correct Answer: c) Greater than either individual wave

Explanation: The amplitudes of the waves add together during constructive interference.

MCQ No. 56

Destructive interference occurs when two waves are:

a) In phase

b) Out of phase by 180°

c) Moving in different media

d) Perpendicular to each other

Correct Answer: b) Out of phase by 180°

Explanation: When two waves differ in phase by 180°, they tend to cancel each other.

MCQ No. 57

Complete destructive interference between two waves of equal amplitude produces:

a) Maximum intensity

b) Zero resultant amplitude

c) Double amplitude

d) Higher frequency

Correct Answer: b) Zero resultant amplitude

Explanation: Equal amplitudes in opposite phase completely cancel each other.

MCQ No. 58

For constructive interference, the path difference between two coherent waves is:

a) λ/2

b) λ

c) λ/4

d) 3λ/2

Correct Answer: b) λ

Explanation: Constructive interference occurs when the path difference is an integral multiple of the wavelength.

MCQ No. 59

For destructive interference, the path difference is:

a) nλ

b) (2n + 1)λ/2

c) 2nλ

d) 4nλ

Correct Answer: b) (2n + 1)λ/2

Explanation: An odd multiple of half a wavelength produces destructive interference.

MCQ No. 60

Beats are produced when two sound waves have:

a) Exactly the same frequency

b) Slightly different frequencies

c) Very large amplitudes

d) Different speeds only

Correct Answer: b) Slightly different frequencies

Explanation: Beats result from the superposition of two sound waves with nearly equal frequencies.

MCQ No. 61

Beat frequency is equal to:

a) f₁ + f₂

b) |f₁ − f₂|

c) f₁ × f₂

d) f₁/f₂

Correct Answer: b) |f₁ − f₂|

Explanation: Beat frequency is the absolute difference between the frequencies of the two waves.

MCQ No. 62

If two tuning forks have frequencies 256 Hz and 260 Hz, the beat frequency is:

a) 2 Hz

b) 4 Hz

c) 6 Hz

d) 8 Hz

Correct Answer: b) 4 Hz

Explanation: Beat frequency = |260 − 256| = 4 Hz.

MCQ No. 63

Beats are heard as periodic changes in:

a) Pitch only

b) Loudness

c) Wavelength

d) Wave speed

Correct Answer: b) Loudness

Explanation: Beats cause alternate increases and decreases in sound intensity.

MCQ No. 64

Standing waves are formed by the superposition of:

a) Two waves moving in the same direction

b) Two waves of equal frequency and amplitude traveling in opposite directions

c) Electromagnetic waves only

d) Two waves of different frequencies

Correct Answer: b) Two waves of equal frequency and amplitude traveling in opposite directions

Explanation: Reflection of a progressive wave produces a standing wave.

MCQ No. 65

A standing wave transfers:

a) Mass

b) Energy continuously

c) No net energy

d) Electric charge

Correct Answer: c) No net energy

Explanation: Standing waves store energy locally without transferring it along the medium.

MCQ No. 66

A point in a standing wave where displacement is always zero is called:

a) Crest

b) Antinode

c) Node

d) Compression

Correct Answer: c) Node

Explanation: A node remains at rest throughout the vibration.

MCQ No. 67

A point where the displacement is maximum in a standing wave is called:

a) Node

b) Crest

c) Antinode

d) Rarefaction

Correct Answer: c) Antinode

Explanation: An antinode experiences the maximum amplitude of vibration.

MCQ No. 68

The distance between two consecutive nodes is:

a) λ

b) λ/2

c) λ/4

d) 2λ

Correct Answer: b) λ/2

Explanation: Adjacent nodes are separated by half a wavelength.

MCQ No. 69

The distance between a node and the nearest antinode is:

a) λ

b) λ/2

c) λ/4

d) λ/8

Correct Answer: c) λ/4

Explanation: A node and its nearest antinode are separated by one-quarter of a wavelength.

MCQ No. 70

In a standing wave, all particles between two consecutive nodes:

a) Vibrate with the same frequency

b) Have different frequencies

c) Remain at rest

d) Move in opposite directions continuously

Correct Answer: a) Vibrate with the same frequency

Explanation: Although their amplitudes differ, all particles vibrate with the same frequency.

MCQ No. 71

The amplitude of vibration at a node is:

a) Maximum

b) Minimum but not zero

c) Zero

d) Infinite

Correct Answer: c) Zero

Explanation: Nodes are stationary points.

MCQ No. 72

The amplitude at an antinode is:

a) Zero

b) Minimum

c) Maximum

d) Equal to half the wavelength

Correct Answer: c) Maximum

Explanation: Antinodes are the points of greatest vibration.

MCQ No. 73

Which phenomenon is used to explain the formation of standing waves?

a) Reflection only

b) Refraction only

c) Superposition of incident and reflected waves

d) Diffraction only

Correct Answer: c) Superposition of incident and reflected waves

Explanation: Standing waves result from interference between incident and reflected waves.

MCQ No. 74

The interference pattern produced by coherent sources is:

a) Temporary and unstable

b) Permanent and stable

c) Completely random

d) Invisible

Correct Answer: b) Permanent and stable

Explanation: Constant phase difference produces a stable interference pattern.

MCQ No. 75

Which statement is correct?

a) Beats are produced by coherent sources of the same frequency.

b) Standing waves transfer energy from one end to another.

c) Constructive interference increases the resultant amplitude.

d) Nodes are points of maximum displacement.

Correct Answer: c) Constructive interference increases the resultant amplitude.

Explanation: During constructive interference, wave amplitudes add together, producing a larger resultant amplitude. Standing waves do not transfer net energy, nodes have zero displacement, and beats require slightly different frequencies.

MCQs 76–100 – Vibrating Strings, Organ Pipes, Doppler Effect, Ultrasound & Applications

MCQ No. 76

The lowest frequency at which a stretched string vibrates is called its:

a) Overtone

b) Harmonic

c) Fundamental frequency

d) Resonance frequency

Correct Answer: c) Fundamental frequency

Explanation: The fundamental frequency is the lowest natural frequency and is also known as the first harmonic.

MCQ No. 77

The fundamental frequency of a vibrating string is also known as the:

a) Second harmonic

b) First harmonic

c) First overtone

d) Third harmonic

Correct Answer: b) First harmonic

Explanation: The first harmonic is the fundamental mode of vibration.

MCQ No. 78

The frequency of the second harmonic of a string is:

a) Equal to the fundamental frequency

b) Half the fundamental frequency

c) Twice the fundamental frequency

d) Three times the fundamental frequency

Correct Answer: c) Twice the fundamental frequency

Explanation: The second harmonic has a frequency equal to twice the fundamental frequency.

MCQ No. 79

The first overtone in a stretched string is:

a) First harmonic

b) Second harmonic

c) Third harmonic

d) Fourth harmonic

Correct Answer: b) Second harmonic

Explanation: The first overtone corresponds to the second harmonic.

MCQ No. 80

The frequency of the third harmonic is:

a) $f$

b) $2f$

c) $3f$

d) $4f$

Correct Answer: c) $3 f$

Explanation: The nth harmonic has a frequency equal to $nf$ .

MCQ No. 81

In an open organ pipe, both ends are:

a) Nodes

b) Antinodes

c) Closed

d) Fixed

Correct Answer: b) Antinodes

Explanation: Air at both open ends vibrates freely, producing displacement antinodes.

MCQ No. 82

In a closed organ pipe, the closed end is always a:

a) Crest

b) Antinode

c) Node

d) Compression

Correct Answer: c) Node

Explanation: Air cannot move at the closed end, so a displacement node is formed.

MCQ No. 83

The open end of a closed organ pipe is always:

a) Node

b) Antinode

c) Compression

d) Rarefaction

Correct Answer: b) Antinode

Explanation: The air at the open end vibrates with maximum amplitude.

MCQ No. 84

Which harmonics are present in a closed organ pipe?

a) Even harmonics only

b) Odd harmonics only

c) All harmonics

d) No harmonics

Correct Answer: b) Odd harmonics only

Explanation: A closed organ pipe supports only odd harmonics.

MCQ No. 85

An open organ pipe supports:

a) Odd harmonics only

b) Even harmonics only

c) All harmonics

d) No harmonics

Correct Answer: c) All harmonics

Explanation: Both even and odd harmonics are produced in an open organ pipe.

MCQ No. 86

The apparent change in the frequency of sound due to relative motion between the source and the observer is known as:

a) Interference

b) Resonance

c) Doppler Effect

d) Diffraction

Correct Answer: c) Doppler Effect

Explanation: The Doppler Effect changes the observed frequency when there is relative motion.

MCQ No. 87

If a sound source moves toward a stationary observer, the observed frequency:

a) Decreases

b) Remains constant

c) Increases

d) Becomes zero

Correct Answer: c) Increases

Explanation: The sound waves are compressed, resulting in a higher observed frequency.

MCQ No. 88

If a sound source moves away from an observer, the observed frequency:

a) Increases

b) Decreases

c) Remains unchanged

d) Doubles

Correct Answer: b) Decreases

Explanation: The sound waves spread farther apart, lowering the observed frequency.

MCQ No. 89

The pitch of the siren of an approaching ambulance appears:

a) Lower

b) Higher

c) Unchanged

d) Zero

Correct Answer: b) Higher

Explanation: Due to the Doppler Effect, the observed frequency increases as the ambulance approaches.

MCQ No. 90

Ultrasound refers to sound waves having frequencies:

a) Less than 20 Hz

b) Between 20 Hz and 20 kHz

c) Greater than 20 kHz

d) Equal to 20 Hz

Correct Answer: c) Greater than 20 kHz

Explanation: Ultrasound has frequencies above the upper limit of human hearing.

MCQ No. 91

The audible range of the human ear is approximately:

a) 1 Hz – 100 Hz

b) 20 Hz – 20 kHz

c) 20 kHz – 200 kHz

d) 100 Hz – 1 MHz

Correct Answer: b) 20 Hz – 20 kHz

Explanation: Healthy human ears can generally hear sounds within this frequency range.

MCQ No. 92

Ultrasound is commonly used in medicine to:

a) Produce X-rays

b) Diagnose internal organs

c) Measure electric current

d) Detect radio waves

Correct Answer: b) Diagnose internal organs

Explanation: Ultrasonic imaging provides safe, non-invasive images of internal body structures.

MCQ No. 93

SONAR is primarily used to:

a) Measure atmospheric pressure

b) Detect underwater objects

c) Generate electricity

d) Measure light intensity

Correct Answer: b) Detect underwater objects

Explanation: SONAR uses ultrasonic waves to locate underwater objects and measure depth.

MCQ No. 94

SONAR works on the principle of:

a) Reflection of sound waves

b) Refraction of light

c) Electromagnetic induction

d) Photoelectric effect

Correct Answer: a) Reflection of sound waves

Explanation: SONAR detects echoes reflected from underwater objects.

MCQ No. 95

Bats locate insects during flight by using:

a) Infrared radiation

b) Radar

c) Ultrasonic waves

d) Visible light

Correct Answer: c) Ultrasonic waves

Explanation: Bats use echolocation by emitting ultrasonic waves and detecting their echoes.

MCQ No. 96

Which animal also uses ultrasonic waves for navigation?

a) Cow

b) Dolphin

c) Horse

d) Camel

Correct Answer: b) Dolphin

Explanation: Dolphins use ultrasonic echolocation to navigate and hunt underwater.

MCQ No. 97

The SI unit of frequency is:

a) Meter

b) Hertz

c) Second

d) Joule

Correct Answer: b) Hertz

Explanation: Frequency is measured in hertz (Hz), where one hertz equals one cycle per second.

MCQ No. 98

Which quantity remains unchanged when a wave enters another medium?

a) Speed

b) Wavelength

c) Frequency

d) Amplitude

Correct Answer: c) Frequency

Explanation: The frequency is determined by the source and remains constant when the wave passes into another medium.

MCQ No. 99

When the speed of a wave changes on entering another medium, its ______ changes accordingly.

a) Frequency only

b) Wavelength

c) Time period only

d) Amplitude only

Correct Answer: b) Wavelength

Explanation: Since $v = f\lambda$ and frequency remains constant, the wavelength changes with speed.

MCQ No. 100

Which of the following statements is correct?

a) Sound waves can travel through a vacuum.

b) Closed organ pipes produce all harmonics.

c) The Doppler Effect changes the apparent frequency due to relative motion between the source and the observer.

d) Ultrasound has a frequency below 20 Hz.

Correct Answer: c) The Doppler Effect changes the apparent frequency due to relative motion between the source and the observer.

Explanation: The Doppler Effect explains the apparent increase or decrease in frequency caused by relative motion. Sound requires a material medium, closed organ pipes support only odd harmonics, and ultrasound has frequencies greater than 20 kHz.