Waves

Waves MDCAT MCQs with answers

121 past paper MCQs from Physics unit 6, Waves, across 11 topics. They are arranged topic by topic; bigger topics show a sample here and link to their full set and to study notes. Tap “Show answer” for the correct option and a short solution.

Practise as a quiz

Wave Motion and Progressive Waves

1.Mechanical waves are not produced in: (MDCAT 2022)

  1. electric and magnetic fields
  2. springs
  3. ropes
  4. water
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Correct answer: (a) electric and magnetic fields

A mechanical wave needs a material medium; a disturbance of the electric and magnetic fields travels without one.

2.Mechanical waves cannot travel through outer space because they: (UHS MDCAT 2025)

  1. have low speed in vacuum
  2. disperse in space due to long wavelength
  3. lose frequency in the absence of air
  4. lose transmission without interacting particles
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Correct answer: (d) lose transmission without interacting particles

A mechanical wave is carried by the particles of a medium, and space has none to pass it on.

3.What is the necessary condition of a wave motion? (KMU MDCAT 2025)

  1. The medium must be elastic
  2. The medium must be inelastic
  3. The particles of the medium must be independent of each other
  4. The particles of the medium must not be dependent on each other
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Correct answer: (a) The medium must be elastic

A wave passes on because each displaced particle is pulled back and pulls its neighbour, which needs an elastic medium.

All 11 Wave Motion and Progressive Waves MCQs → Wave Motion and Progressive Waves notes →

Characteristics of a Wave and Wave Speed

4.In a ripple tank 40 waves pass through a certain point in one second. If the wavelength of the waves is 5 cm, then find the speed of the wave. (MDCAT 2020)

  1. $2\ \mathrm{m\,s^{-1}}$
  2. $8\ \mathrm{m\,s^{-1}}$
  3. $20\ \mathrm{m\,s^{-1}}$
  4. $200\ \mathrm{m\,s^{-1}}$
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Correct answer: (a) $2\ \mathrm{m\,s^{-1}}$

$v=f\lambda=40\times0.05=2\ \mathrm{m\,s^{-1}}$.

5.The product of frequency and time period is equal to: (MDCAT 2020)

  1. 1
  2. 2
  3. 0
  4. $1/2$
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Correct answer: (a) 1

$T=1/f$, so $fT=1$.

6.The shortest distance between any two points in phase on a wave is called the: (MDCAT 2022)

  1. displacement
  2. amplitude
  3. wavelength
  4. frequency
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Correct answer: (c) wavelength

That distance is one wavelength.

All 37 Characteristics of a Wave and Wave Speed MCQs → Characteristics of a Wave and Wave Speed notes →

Transverse and Longitudinal Waves

7.If transverse waves are passing through a medium, then the particles of the medium: (MDCAT 2023)

  1. remain stationary
  2. move away with the wave
  3. move towards the source
  4. move in simple harmonic motion
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Correct answer: (d) move in simple harmonic motion

Each particle oscillates about its own mean position at right angles to the direction of travel.

8.The motion of transverse waves involves particle's vibration: (SIBA MDCAT 2025)

  1. Along the wave direction
  2. Opposite to energy flow
  3. Perpendicular to wave propagation
  4. In random direction at every point
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Correct answer: (c) Perpendicular to wave propagation

In a transverse wave the particles move at right angles to the direction the wave travels.

9.Which type of waves can be polarized? (KMU MDCAT 2024)

  1. Longitudinal waves
  2. Mechanical waves
  3. Sound waves
  4. Transverse waves
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Correct answer: (d) Transverse waves

Only a transverse wave has a vibration direction to single out, so only it can be polarized.

All 11 Transverse and Longitudinal Waves MCQs → Transverse and Longitudinal Waves notes →

Speed of Sound: Newton’s Formula and Laplace’s Correction

10.Newton's original formula underestimated speed of sound in air because he: (SIBA MDCAT 2025)

  1. Ignored viscosity
  2. Assumed isothermal
  3. Considered vacuum conditions
  4. Assumed adiabatic
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Correct answer: (b) Assumed isothermal

Newton took the compressions to be isothermal; Laplace corrected them to adiabatic and got the right speed.

11.The option that shows the conditions used by Laplace for connecting the velocity of sound is options medium used thermodynamics process 1 solid adiabatic 2 liquids isobaric 3 gas adiabatic 4 gas isothermal (SZABMU MDCAT 2025)

  1. 1
  2. 2
  3. 3
  4. 4
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Correct answer: (c) 3

Laplace took the compressions and rarefactions in a gas to be too quick for heat to escape, that is adiabatic.

12.Speed of sound in solid is greater than in air because ratio: (NUMS MDCAT 2024)

  1. (√E/ρ) solid < (√E/ρ) air
  2. (√E/ρ) solid > (√E/ρ) air
  3. (√E/ρ) solid = (√E/ρ) air
  4. (√E/ρ) solid ≤ (√E/ρ) air
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Correct answer: (b) (√E/ρ) solid > (√E/ρ) air

$v=\sqrt{E/\rho}$, and a solid gains far more in elasticity than it loses to density.

Speed of Sound: Newton’s Formula and Laplace’s Correction notes →

Factors Affecting the Speed of Sound in Air

13.The speed of sound in an ideal gas depends upon its: (MDCAT 2023)

  1. temperature
  2. frequency
  3. amplitude
  4. wavelength
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Correct answer: (a) temperature

$v\propto\sqrt{T}$; the frequency, amplitude and wavelength of the sound do not change it.

14.Speed of sound in air increases with: (KMU MDCAT 2025)

  1. Higher temperature, higher humidity
  2. Lower temperature, lower humidity
  3. Higher pressure at constant temperature
  4. Higher density at constant elasticity
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Correct answer: (a) Higher temperature, higher humidity

Sound travels faster in warmer air, and water vapour is lighter than the air it displaces, so humidity helps too.

15.If the speed of sound is measured at sea level and at the top of a mountain, both at the same temperature, it will be: (SZABMU MDCAT 2025)

  1. Greater at sea level
  2. Greater at the mountain top
  3. The same at both places
  4. Greater where the air is denser
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Correct answer: (c) The same at both places

The speed of sound depends on the temperature of the air, not on its pressure or density.

All 11 Factors Affecting the Speed of Sound in Air MCQs → Factors Affecting the Speed of Sound in Air notes →

Superposition and Interference of Sound Waves

16.If two speakers emit sound at same frequency and phase, maximum loudness occurs when: (UHS MDCAT 2025)

  1. Path difference = √2
  2. Path difference = λ
  3. Path difference = λ/4
  4. Path difference = 3λ/43
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Correct answer: (b) Path difference = λ

Constructive interference needs a path difference of a whole number of wavelengths.

17.Two waves identical traveling in the same medium are superposed: (NUMS MDCAT 2025)

  1. Interference
  2. Diffraction
  3. Reflection
  4. Refraction
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Correct answer: (a) Interference

Two waves of the same kind crossing in one medium add displacement to displacement, which is interference.

18.The path difference between two sound waves coming from a coherent source of wavelength 50 cm at a point is 100 cm. The superposition of the waves at that point produces: (SIBA MDCAT 2025)

  1. Beats
  2. Echo
  3. Loudness
  4. Silence
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Correct answer: (c) Loudness

A path difference of $100\,\mathrm{cm}$ is exactly two wavelengths, so the waves arrive in step and reinforce.

All 9 Superposition and Interference of Sound Waves MCQs → Superposition and Interference of Sound Waves notes →

Stationary Waves, Nodes and Antinodes

19.Which one of the following is INCORRECT about the nodes when a string is plucked? (MDCAT 2024)

  1. the amplitude of vibration is zero
  2. they do not move along the string
  3. they are produced at the fixed ends of the string
  4. the distance between consecutive nodes is one wavelength
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Correct answer: (d) the distance between consecutive nodes is one wavelength

Consecutive nodes are half a wavelength apart, not a whole wavelength.

20.Which one of the following does not cause stationary waves? (MDCAT 2024)

  1. two waves of equal frequency
  2. two waves of the same speed
  3. two waves of unequal amplitude
  4. two waves travelling in opposite directions
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Correct answer: (c) two waves of unequal amplitude

Stationary waves need two waves of equal amplitude; unequal amplitudes leave a travelling wave over the pattern.

21.In a stationary wave the point that undergoes zero acceleration is: (SZABMU MDCAT 2025)

  1. Node
  2. Antinode
  3. Midpoint between node and antinode
  4. Every point along the wave
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Correct answer: (a) Node

A node never moves, so its displacement, velocity and acceleration are all zero.

All 9 Stationary Waves, Nodes and Antinodes MCQs → Stationary Waves, Nodes and Antinodes notes →

Stationary Waves in a Stretched String

22.Stationary waves are formed in a stretched string of 2m length, such that two vibrating loops are formed. The distance between consecutive nodes formed is: (SZABMU MDCAT 2025)

  1. 0.5 m
  2. 1 m
  3. 2 m
  4. 3 m
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Correct answer: (b) 1 m

Two loops in $2\,\mathrm{m}$ make each loop $1\,\mathrm{m}$, and a loop runs from one node to the next.

23.Which one of the following is INCORRECT about the nodes when the string is plucked; (UHS MDCAT 2024)

  1. Amplitude of vibration is zero
  2. Do not move along the string
  3. Produced at the fixed ends of strings
  4. Distance between consecutive nodes is 1 wavelength
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Correct answer: (d) Distance between consecutive nodes is 1 wavelength

Consecutive nodes are half a wavelength apart, not a whole one.

24.When a standing wave is set up on a string fixed at both ends, which of the following statements is true? (PMC Practice 2021)

  1. Sum of the number of antinodes and the number of nodes is always even
  2. Wavelength = length string / number of nodes
  3. The shape of the string at any instant shows a symmetry about the midpoint of the string
  4. Frequency = number of nodes x fundamental frequency
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Correct answer: (c) The shape of the string at any instant shows a symmetry about the midpoint of the string

The pattern of loops between the fixed ends is symmetrical about the middle of the string.

25.The speed ‘v’ of the waves in the string depends upon the tension, F, of the string and m, the mass per unit length of the string. It is given by: (PMC Practice 2021)

  1. v2 = F/m
  2. v = F/m
  3. v x m = F
  4. v = F x m
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Correct answer: (a) v2 = F/m

The speed of a wave on a stretched string is $\sqrt{F/m}$.

Stationary Waves in a Stretched String notes →

Stationary Waves in Organ Pipes

26.For a certain organ pipe three successive resonance frequencies are \$425\$, \$595\$ and \$765\,\mathrm{Hz}\$. Taking the speed of sound as \$340\,\mathrm{m\,s^{-1}}\$, the pipe is: (UHS MDCAT 2017)

  1. a closed pipe of length $1\,\mathrm{m}$
  2. a closed pipe of length $2\,\mathrm{m}$
  3. an open pipe of length $1\,\mathrm{m}$
  4. an open pipe of length $2\,\mathrm{m}$
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Correct answer: (a) a closed pipe of length $1\,\mathrm{m}$

The spacing is $170\,\mathrm{Hz}$, and the three are $5$, $7$ and $9$ times $85\,\mathrm{Hz}$. Only odd harmonics appear, so the pipe is closed, and $85=v/4L$ gives $L=1\,\mathrm{m}$.

27.A pipe open at both ends resonates at a fundamental frequency fo. When one end is covered and the pipe is again made to resonate, the fundamental frequency is fc. Which of the following expressions describes the relationship between these two resonants? (PMC MDCAT 2022)

  1. fc = fo
  2. 2xfc = fo
  3. fc = 2fo
  4. none
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Correct answer: (b) 2xfc = fo

An open pipe sounds $v/2L$ and a closed one $v/4L$, so the open note is twice the closed.

28.For a certain organ pipe, three successive resonance frequencies are observed at 425, 595, and 765 Hz. The speed of the sound in air is 340 m/s. The pipe is: (UHS MDCAT 2017)

  1. Closed pipe of length 1 m
  2. Closed pipe of length 2 m
  3. Open pipe of length 1 m
  4. Open pipe of length 2 m
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Correct answer: (a) Closed pipe of length 1 m

The frequencies differ by $170\,\mathrm{Hz}$ and are odd multiples of $85\,\mathrm{Hz}$, so the pipe is closed and $340/(4\times85)$ is $1\,\mathrm{m}$.

Stationary Waves in Organ Pipes notes →

Simple Harmonic Motion

29.When will the oscillations of a pendulum stop in the absence of resistive forces? (MDCAT 2022)

  1. never
  2. after 10 minutes
  3. in 10 minutes
  4. immediately
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Correct answer: (a) never

With nothing to take its energy away the motion is undamped and continues indefinitely.

30.Reducing the mass $M$ of a suspended body to one fourth will change the frequency of oscillation to: (MDCAT 2022)

  1. one fourth
  2. double
  3. quadruple
  4. half
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Correct answer: (b) double

$f=\dfrac{1}{2\pi}\sqrt{k/m}$, so a quarter of the mass doubles the frequency.

31.If the length of a second's pendulum becomes four times, then its time period will become: (MDCAT 2023)

  1. four times
  2. two times
  3. half
  4. one fourth
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Correct answer: (b) two times

$T=2\pi\sqrt{l/g}$, so $T$ goes as the square root of the length.

All 22 Simple Harmonic Motion MCQs → Simple Harmonic Motion notes →

Circular Motion and SHM

32.A particle is moving in a uniform circular path whose projection is executing simple harmonic motion on horizontal diameter. The ratio of instantaneous velocity to the maximum velocity of the projection while passing through the center is: (SZABMU MDCAT 2025)

  1. 1 : 1
  2. 1 : 2
  3. 2 : 1
  4. 1 : 4
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Correct answer: (a) 1 : 1

The projection is fastest as it passes the centre, so the instantaneous speed there is the maximum speed.

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