Lesson 5.2.1

5.2.1 Wavefronts, coherence and phase difference Quiz: Pearson Edexcel Physics, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 5.2.1, Wavefronts, coherence and phase difference: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 5: Waves and Particle Nature of Light, written with Revision Ninja.

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The 20 questions

  1. What is a wavefront?

    • A surface where the wave amplitude is always zero
    • The path along which energy is absorbed by a detector
    • A line or surface joining all points on a wave that are in phase
    • A line joining the points of maximum displacement only

  2. When are two sources described as coherent?

    • They have the same amplitude and wavelength only
    • They have the same speed in air
    • They have the same frequency and a constant phase difference between them
    • They have different frequencies but the same intensity

  3. Under what condition does constructive interference occur at a point?

    • The path difference is zero only
    • The path difference is a whole number of wavelengths
    • The path difference is an odd number of half-wavelengths
    • The path difference is a quarter of a wavelength

  4. Under what condition does destructive interference occur at a point?

    • The path difference is exactly two wavelengths
    • The path difference is zero
    • The path difference is a whole number of wavelengths
    • The path difference is an odd number of half-wavelengths

  5. What does the principle of superposition state?

    • The resultant displacement is the average of the individual displacements
    • The resultant displacement at a point is the sum of the displacements of the individual waves at that point
    • The resultant displacement is always the largest individual displacement
    • The resultant displacement is the product of the individual displacements

  6. What is interference?

    • The change in speed of a wave when it enters a new medium
    • The reflection of a wave at a boundary between two media
    • The superposition of two or more coherent waves, producing regions of reinforcement and cancellation
    • The bending of a wave around an obstacle

  7. A path difference of half a wavelength corresponds to what phase difference?

    • 180 degrees
    • 360 degrees
    • 0 degrees
    • 90 degrees

  8. Two in-phase coherent sources have wavelength 0.30 m. At a point the path difference is 0.90 m. What is observed?

    • Maximum, constructive interference
    • Intermediate amplitude equal to half the maximum
    • No interference, because the path difference is large
    • Minimum, destructive interference

  9. Two coherent waves have path difference 0.15 m and wavelength 0.60 m. What is their phase difference?

    • 90 degrees
    • 45 degrees
    • 270 degrees
    • 180 degrees

  10. Two coherent waves of wavelength 0.60 m have path difference 0.45 m. What is their phase difference?

    • 180 degrees
    • 90 degrees
    • 135 degrees
    • 270 degrees

  11. Two in-phase sound sources emit at 500 Hz in air where the speed is 340 m/s. At a point the path difference is 0.34 m. What is observed?

    • Intermediate amplitude, equal to the sum of the two amplitudes
    • Constructive interference, giving a maximum, because the path difference is a whole number of wavelengths
    • No interference, because sound sources cannot be coherent
    • Destructive interference, giving a minimum, because the path difference is half a wavelength

  12. Two coherent waves each have amplitude 3.0 mm and arrive in phase at a point. What is the resultant amplitude?

    • 0 mm
    • 6.0 mm
    • 9.0 mm
    • 3.0 mm

  13. Two coherent waves of amplitudes 4.0 and 1.0 arrive in antiphase at a point. What is the resultant amplitude?

    • 2.5
    • 0
    • 5.0
    • 3.0

  14. Light of wavelength 600 nm from two coherent sources arrives at a point with path difference 1.5 micrometres. What is observed?

    • Constructive interference, since the path difference is a whole number of wavelengths
    • Constructive interference, since the path difference is 1.5 micrometres
    • Destructive interference, since the path difference is 2.5 wavelengths
    • No interference, since the wavelength is too small

  15. The distance between adjacent plane wavefronts of a wave is 0.050 m. What is the wavelength?

    • 0.050 m
    • 340 m
    • 0.10 m
    • 0.025 m

  16. Two identical lamps placed side by side are not coherent sources. Why?

    • Their light is emitted by independent atoms, so there is no constant phase difference between the two sources
    • Lamps cannot emit light of a single wavelength
    • Lamps always emit light at different frequencies from each other
    • Lamps are too bright for their light to interfere

  17. Two in-phase coherent sources have wavelength 0.20 m. Point P is 2.30 m from one source and 2.00 m from the other. What is observed at P?

    • Destructive interference, since the path difference is 1.5 wavelengths
    • Constructive interference, since the path difference is 0.30 m
    • Intermediate amplitude, since 2.30 m is not a multiple of 0.20 m
    • Constructive interference, since the path difference is 1.5 wavelengths

  18. Two in-phase speakers emit a 680 Hz tone in air at 340 m/s. At a point the path difference is 1.0 m. What is observed?

    • Intermediate amplitude of 1.5 times the single-speaker amplitude
    • The result cannot be found without knowing the amplitudes
    • Destructive interference, since the path difference is two wavelengths
    • Constructive interference, since the path difference is two wavelengths

  19. Two coherent waves have a phase difference of 2.0 radians. What is their path difference in wavelengths?

    • 0.13 wavelength
    • 0.32 wavelength
    • 2.0 wavelengths
    • 0.50 wavelength

  20. A student says destructive interference means energy is destroyed at the minima. Which evaluation is correct?

    • Incorrect, because destructive interference never occurs for sound waves
    • Correct, because energy is destroyed at the minima of the pattern
    • Correct, because the wave loses its amplitude permanently at minima
    • Incorrect, because energy is redistributed to the regions of constructive interference, so total energy is conserved

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