Lesson 3.3.2.1

3.3.2.1 Interference Quiz: AQA Physics, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson 3.3.2.1, Interference: 20 multiple choice questions for the AQA Physics (7408), Unit 3: Waves, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. What property must two wave sources share to be described as coherent?

    • Constant phase difference
    • Equal amplitude
    • Variable frequency
    • Constant velocity

  2. What path difference between two coherent waves produces constructive interference?

    • Odd quarter wavelengths
    • Half wavelengths
    • Whole wavelengths
    • Zero frequency

  3. What path difference gives destructive interference?

    • n λ
    • (n + 1/2) λ
    • λ/4 exactly
    • 2 n λ only

  4. What is the formula for fringe spacing in Young's double-slit experiment?

    • w = λs/D
    • w = λ/(Ds)
    • w = λD/s
    • w = Ds/λ

  5. What characterises light that is described as monochromatic?

    • Multiple frequencies
    • Constant amplitude
    • Single velocity
    • Single wavelength

  6. Why is the central fringe white when white light passes through double slits?

    • Maximum dispersion
    • Single wavelength
    • Total internal reflection
    • Zero path difference

  7. Which two properties make lasers ideal for double-slit interference experiments?

    • Monochromatic and unpolarised
    • Incoherent and bright
    • Monochromatic and coherent
    • Polychromatic and coherent

  8. Light of wavelength 600 nm passes through slits 0.30 mm apart, with a screen 1.5 m away. What is the fringe spacing?

    • 0.03 mm
    • 30 mm
    • 0.3 mm
    • 3.0 mm

  9. Fringes separated by 2.0 mm are seen on a screen 2.0 m away from slits 0.4 mm apart. What is the wavelength?

    • 40 nm
    • 0.4 nm
    • 4 μm
    • 400 nm

  10. If the slit separation is doubled, what happens to the fringe spacing?

    • It quadruples
    • It halves
    • It doubles
    • It is unchanged

  11. If the screen is moved further from the slits, what happens to the fringe spacing?

    • It increases
    • It decreases
    • It is unchanged
    • It becomes zero

  12. What is observed when two in-phase sources have a path difference of 1.5 λ?

    • Total refraction
    • Constructive interference
    • No diffraction
    • Destructive interference

  13. What is observed when two in-phase sources have a path difference of 2.0 λ?

    • Destructive interference
    • Total absorption
    • Constructive interference
    • Polarisation

  14. Two in-phase 680 Hz loudspeakers emit sound at 340 m/s with path difference 0.25 m. What occurs?

    • Destructive interference
    • Resonance
    • Constructive interference
    • Refraction

  15. What type of interference occurs when microwaves of wavelength 3.0 cm have a path difference of 6.0 cm?

    • Total internal reflection
    • Diffraction grating
    • Destructive interference
    • Constructive interference

  16. What causes a diffraction grating to separate white light into spectral orders?

    • Polarisation of light
    • Wavelength-dependent interference
    • Material dispersion
    • Refraction at boundaries

  17. A double slit with spacing 1.0 mm gives fringe spacing 0.50 mm on a screen at 1.0 m. What is the wavelength?

    • 125 nm
    • 250 nm
    • 500 nm
    • 1.25 μm

  18. What primary hazard is associated with using lasers during light interference practicals?

    • Eye damage
    • Ionising radiation
    • Electric shock
    • Skin burns

  19. What happens to double-slit fringe spacing when the light wavelength increases?

    • Spacing increases
    • Spacing remains constant
    • Fringes disappear
    • Spacing decreases

  20. What feature of coherent light sources ensures a stable interference pattern on a screen?

    • Identical speed
    • Maximum brightness
    • Constant phase difference
    • Variable wavelength

All AQA Physics quizzes