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 did Thomson's measurements of cathode rays show?

    • the rays had the same charge-to-mass ratio as protons
    • the rays were electromagnetic waves with no mass
    • the rays were positive ions with the same mass as hydrogen
    • the rays were charged particles with a charge-to-mass ratio much larger than that of hydrogen ions

  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 did Millikan's results show about electric charge?

    • charges were whole-number multiples of about 1.6 x 10^-19 C, so charge is quantised
    • charges were whole-number multiples of about 9.1 x 10^-31 C
    • charges took any continuous value with no minimum
    • charges were multiples of about 6.6 x 10^-34 C

  6. Why was Newton's corpuscular theory of light preferred for a time?

    • it explained rectilinear propagation and reflection simply, and Newton's authority favoured it
    • it required no medium, which was later detected
    • it predicted interference fringes that were later observed
    • it explained the photoelectric effect

  7. What did Young's double-slit experiment show about light?

    • that light travels only in straight lines with no diffraction
    • that light produces interference fringes, which supports a wave model
    • that light consists of particles that never interfere
    • that the speed of light depends on the source

  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. Why could classical wave theory not explain the photoelectric effect?

    • the effect requires a strong magnetic field to occur
    • waves cannot carry any energy at all
    • emission depends on frequency rather than intensity, and occurs almost instantly, which waves do not predict
    • electrons are emitted only from liquid surfaces

  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 was the outcome of the Michelson-Morley experiment?

    • a large fringe shift showed the Earth moves through the ether at 30 km/s
    • no fringe shift was detected, so no absolute motion through an ether could be measured
    • it measured the speed of light to be twice its accepted value
    • the apparatus failed because light has no wavelength

  17. Which postulate of Einstein's special relativity concerns the speed of light?

    • physical laws differ between inertial frames
    • the speed of light in free space is the same in all inertial frames
    • the speed of light depends on the speed of its source
    • the speed of light changes with gravity

  18. What did Bertozzi's experiment show?

    • the speed of electrons does not depend on their energy
    • electrons lose mass as they accelerate
    • the kinetic energy of fast electrons increases with speed as relativity predicts, not as classical physics predicts
    • electrons travel faster than the speed of light

  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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