Superposition and Interference of Sound Waves

Superposition and Interference of Sound Waves MDCAT MCQs with answers

9 past paper MCQs on Superposition and Interference of Sound Waves, from the Waves unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.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.

2.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.

3.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.

4.The phenomenon of interference of sound waves requires: (SIBA MDCAT 2025)

  1. Two sources with different frequencies
  2. Two coherent sources
  3. A single source
  4. A single source and a reflecting surface
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Correct answer: (b) Two coherent sources

A steady pattern needs two sources of the same frequency holding a constant phase relation.

5.When two identical waves arrive in phase at same point and in a region at the same time the resultant displacement is equal to (SZABMU MDCAT 2025)

  1. Displacement of a single wave
  2. Difference of their displacements
  3. Sum of their displacements
  4. Product of their displacements
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Correct answer: (c) Sum of their displacements

Waves in step add displacement to displacement, which is constructive interference.

6.What happens when two waves of the same frequency and amplitude meet in phase? (KMU MDCAT 2024)

  1. They cancel each other out resulting in a destructive interference
  2. They combine to form a wave double the amplitude, resulting in constructive interference
  3. They produce a wave with zero amplitude
  4. They produce a wave with the same amplitude as the individual waves
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Correct answer: (b) They combine to form a wave double the amplitude, resulting in constructive interference

Crest falls on crest, and the displacements add to give twice the amplitude.

7.According to the principle of superimposition, when 2 or more waves overlap at a point in space, the amplitude of the resultant wave at that point is (KMU MDCAT 2024)

  1. Always zero
  2. The product of the individual wave amplitude
  3. The product of the frequencies of the individual waves
  4. The sum of the amplitudes of the individual waves
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Correct answer: (d) The sum of the amplitudes of the individual waves

The resultant displacement at any point is the sum of the separate displacements there.

8.When two ends of string are struck together simultaneously such that two troughs are traveling towards each other, than at reaching the centre of the string a _ is formed: (PMC MDCAT 2022)

  1. A higher amplitude wave
  2. A Lower amplitude wave
  3. Waves die immediately
  4. Troughs are converted to crests
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Correct answer: (a) A higher amplitude wave

Trough falls on trough, so the displacements add and the wave is twice as deep.

9.Beats can be used to find: (PMC Practice 2021)

  1. Speed
  2. Frequency
  3. Amplitude
  4. Wavelength
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Correct answer: (b) Frequency

The number of beats a second is the difference of the two frequencies, so an unknown note can be measured against a standard.

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