Lesson 3.12

3.12 Turning points: electron discovery, wave-particle duality, relativity Quiz: AQA Physics, Unit 12

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.12, Turning points: electron discovery, wave-particle duality, relativity: 20 multiple choice questions for the AQA Physics (7408), Unit 12: Turning points in physics (A-level option), written with Revision Ninja.

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The 20 questions

  1. In Millikan's oil-drop experiment, what condition holds a charged drop of charge Q stationary between parallel plates?

    • Q/V = mgd
    • QVd = mg
    • QV/d = mg
    • QV/d = mv

  2. Which expression is Stokes' law for the viscous drag on a small sphere of radius r moving at speed v in a fluid of viscosity eta?

    • F = pi eta r v
    • F = 6 pi eta r^2 v
    • F = 6 eta r v / pi
    • F = 6 pi eta r v

  3. What property of cathode rays did J.J. Thomson measure to discover the electron?

    • Rest mass
    • Absolute charge
    • Half-life
    • Specific charge

  4. An electron is accelerated from rest through a potential difference V. Which equation relates its speed to V?

    • m v = e V
    • (1/2) m v^2 = e V
    • m v^2 = e V
    • (1/2) m v = e V

  5. What property of electric charge did Millikan's oil drop experiment prove?

    • Quantisation
    • Continuity
    • Infinite charge
    • Relative charge

  6. What key observation supported Newton's corpuscular theory over Huygens' wave theory?

    • Rectilinear propagation
    • Light polarisation
    • Light diffraction
    • Light interference

  7. What nature of light was demonstrated by Young's double-slit experiment?

    • Quantum nature
    • Wave nature
    • Particle nature
    • Corpuscular nature

  8. Which equation gives the speed of electromagnetic waves in a vacuum in terms of the permeability and permittivity of free space?

    • c = 1 / sqrt(mu0 epsilon0)
    • c = sqrt(mu0 epsilon0)
    • c = mu0 epsilon0
    • c = 1 / (mu0 epsilon0)

  9. Using mu0 = 4 pi x 10^-7 H m^-1 and epsilon0 = 8.85 x 10^-12 F m^-1, what is the speed of light in a vacuum?

    • 3.0 x 10^8 m/s
    • 1.5 x 10^8 m/s
    • 6.0 x 10^8 m/s
    • 3.0 x 10^6 m/s

  10. In the photoelectric effect, photoelectron emission depends primarily on which property of incident light?

    • Light phase
    • Light intensity
    • Light frequency
    • Light amplitude

  11. An electron is accelerated through 100 V from rest. What is its de Broglie wavelength?

    • 1.2 x 10^-7 m
    • 1.2 x 10^-10 m
    • 6.6 x 10^-34 m
    • 1.2 x 10^-13 m

  12. Roughly what accelerating voltage gives electrons a de Broglie wavelength of about 0.1 nm, comparable with atomic sizes?

    • about 1.5 kV
    • about 1.5 MV
    • about 15 V
    • about 150 V

  13. A muon moves at speed 0.8c. What is the time dilation factor?

    • 1.67
    • 0.80
    • 0.60
    • 1.25

  14. A rod moves at 0.6c relative to an observer. What is its observed length as a fraction of its rest length l0?

    • 0.36 l0
    • 1.25 l0
    • 0.6 l0
    • 0.8 l0

  15. What is the energy equivalent of the rest mass of an electron, 9.1 x 10^-31 kg?

    • 0.051 MeV
    • 0.91 MeV
    • 5.1 MeV
    • 0.51 MeV

  16. What outcome was observed in the Michelson-Morley experiment?

    • Large fringe shift
    • Null fringe shift
    • Continuous rotation
    • Frequency doubling

  17. According to Einstein's second postulate of special relativity, what is invariant in all inertial frames?

    • Rest mass
    • Speed of light
    • Kinetic energy
    • Time interval

  18. What relationship did Bertozzi's experiment verify for high-speed electrons?

    • Classical kinetic energy
    • Constant electron speed
    • Relativistic kinetic energy
    • Quantum wave function

  19. A muon has a proper lifetime of 2.2 microseconds and moves at 0.99c. What is its observed mean lifetime?

    • 2.2 microseconds
    • 15.6 microseconds
    • 0.31 microseconds
    • 2.2 seconds

  20. An electron moves at 0.866c. What is its kinetic energy? Take the electron rest energy as 0.51 MeV.

    • 0.26 MeV
    • 0.51 MeV
    • 1.02 MeV
    • 0.77 MeV

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