Interference: past paper questions

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• Question 29May/June 2026, paper 11Multiple choice1 mark

  What is a condition for two sources of waves to produce an interference pattern?

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• Question 28Oct/Nov 2025, paper 11Multiple choice1 markHas a diagram

  A student carries out a double-slit experiment using a laser emitting red light of wavelength of $680\text{ nm}$. The light is incident normally on a double slit.

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• Question 27Oct/Nov 2024, paper 11Multiple choice1 mark

  Three statements about two progressive waves are listed. 1 The waves have the same frequency. 2 The waves have the same amplitude.

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• Question 28Oct/Nov 2023, paper 11Multiple choice1 mark

  Light of wavelength $\lambda$ is emitted from two point sources R and S and falls onto a distant screen. At point P on the screen, the light intensity is zero. What could explain the zero intensity at P?

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• Question 30May/June 2026, paper 11Multiple choice1 markHas a diagram

  Green light of wavelength $550\text{ nm}$ passes through a double slit. This produces an interference pattern with a fringe spacing of $5.0\text{ cm}$ on a screen. Which changes to the experimental arrangement result in a fringe spacing of $2.5\text{ cm}$?

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• Question 28Oct/Nov 2024, paper 11Multiple choice1 mark

  Waves P and Q have the same amplitude. The waves meet in phase at point X and interfere to give a resultant wave with intensity $I$.

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• Question 25Oct/Nov 2023, paper 12Multiple choice1 mark

  What can explain how stationary waves are formed from progressive waves?

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• Question 29May/June 2026, paper 12Multiple choice1 mark

  Waves are emitted by two coherent sources. The two waves meet at point X where they have a constant phase difference of 180°. At point X, the amplitude of one of the waves is $0.50\text{ m}$ and the amplitude of the other wave is $0.30\text{ m}$.

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• Question 28Oct/Nov 2025, paper 13Multiple choice1 markHas a diagram

  A student carries out a double-slit experiment using a laser emitting red light of wavelength of $680\text{ nm}$. The light is incident normally on a double slit.

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• Question 28Oct/Nov 2024, paper 12Multiple choice1 mark

  What happens when two waves superpose at a point?

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• Question 28Oct/Nov 2023, paper 12Multiple choice1 markHas a diagram

  Coherent light of constant wavelength is incident normally on a double slit. Interference fringes are formed on a screen that is a fixed distance from the double slit. The screen is parallel to the double slit.

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• Question 27May/June 2026, paper 13Multiple choice1 mark

  Light from a laser is incident normally on a double slit.

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• Question 4Oct/Nov 2025, paper 22Structured8 marksHas a diagram

  A laser emits visible light of a single frequency in a vacuum. The light is incident normally on a double slit and then forms a pattern of bright and dark fringes on a screen, as shown in Fig. 4.1. The separation of the slits is $1.0\times {10}^{-3}\text{ m}$.

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• Question 28Oct/Nov 2023, paper 13Multiple choice1 markHas a diagram

  Light of a single wavelength is incident normally on a double slit. The slit separation can be varied. A screen is placed a fixed distance away from the double slit.

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• Question 3May/June 2026, paper 22Structured10 marksHas a diagram

  Two oscillating dippers are used to create progressive transverse water waves on the surface of a lake. The waves are shown from above in Figure 3.1. Wave crests are represented by a solid line.

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• Question 6Oct/Nov 2024, paper 21Structured9 marksHas a diagram

  Two coherent sources X and Y of microwaves of frequency $2.5\times {10}^{10}\text{ Hz}$ are a distance of $0.18\text{ m}$ apart in a vacuum, as shown in Fig. 6.1. There is a phase difference of ${90}^{\circ }$ between the waves emitted at the two sources.

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• Question 4Oct/Nov 2023, paper 21Structured9 marksHas a diagram

  State the principle of superposition.

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• Question 31May/June 2025, paper 12Multiple choice1 mark

  Light of a single wavelength is incident normally on a double slit. Interference fringes are observed on a screen. The distance from the double slit to the screen is $0.60\text{ m}$ and the fringe separation is $1.8\text{ mm}$.

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• Question 30May/June 2024, paper 11Multiple choice1 markHas a diagram

  Microwaves are emitted from two sources at points X and Y. The two waves meet at point Z. The diagram shows the paths of the two waves. The waves emitted from points X and Y are coherent. What is a direct consequence of the two waves being coherent?

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• Question 5Oct/Nov 2023, paper 23Structured6 marksHas a diagram

  Two point sources, A and B, produce coherent electromagnetic waves. The waves from A and B are emitted in phase and have wavelength $\lambda$, as shown in Fig. 5.1. The lines on Fig. 5.1 represent wavefronts.

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• Question 28May/June 2025, paper 13Multiple choice1 markHas a diagram

  Electromagnetic waves of equal wavelengths are emitted from two sources, X and Y. The waves are emitted from X and Y with a phase difference of ${180}^{\circ }$.

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• Question 28May/June 2024, paper 12Multiple choice1 mark

  Interference fringes of separation $x$ are observed on a screen at a distance of $1.00\text{ m}$ from a double slit that is illuminated by yellow light of wavelength $600\text{ nm}$.

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• Question 25May/June 2023, paper 11Multiple choice1 mark

  Two progressive waves meet at a point. Which condition must be met for superposition of the waves to occur?

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• Question 29May/June 2025, paper 13Multiple choice1 mark

  Two waves of the same type overlap. When does the principle of superposition apply?

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• Question 27May/June 2024, paper 13Multiple choice1 mark

  Two waves superpose.

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• Question 31May/June 2025, paper 13Multiple choice1 mark

  Light of a single frequency from two coherent sources interferes to produce a pattern of bright and dark fringes on a screen. Which change results in a larger fringe separation?

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• Question 4May/June 2024, paper 23Structured8 marksHas a diagram

  A progressive transverse wave travelling from left to right is shown at an instant in time in Fig. 4.1. R and T are points on the wave. State the phase difference between the points R and T.

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• Question 28May/June 2023, paper 12Multiple choice1 mark

  The diagram shows a view from above of a double-slit interference demonstration. L is a monochromatic light source with a vertical filament. B is a barrier with two narrow vertical slits and S is a screen upon which interference fringes form.

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• Question 28May/June 2023, paper 13Multiple choice1 mark

  Two coherent electromagnetic waves are travelling in a vacuum. The two waves meet at a point. At this point, the two waves have different intensities.

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• Question 3May/June 2025, paper 22Structured8 marksHas a diagram

  Two progressive water waves X and Y travel along a straight line from point A to point B. The variation of displacement of the waves with distance from A at an instant in time is shown in Fig. 3.1.

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