Photoelectric Effect and Electron Diffraction Lab for A Level Physics
Test the photon model of light and the wave behaviour of electrons using threshold experiments, stopping potentials, a Planck graph and measurable diffraction rings.
Learning guide and suggested activities
What this tool shows
Why photoemission depends on photon frequency rather than light intensity alone
How work function, threshold frequency, maximum kinetic energy and stopping potential are linked
How a current–potential curve reveals stopping potential and saturation current
How stopping-potential data can be used to estimate the Planck constant
How accelerating voltage changes electron momentum, de Broglie wavelength and diffraction-ring radius
Why polycrystalline targets produce rings while a single crystal produces spots
OCR A relevance
OCR A H556 Module 4.5.2: the photoelectric effect and photon interactions
OCR A H556 Module 4.5.3: electron diffraction and wave–particle duality
Work function, threshold frequency, stopping potential and the de Broglie relationship
AQA relevance
AQA 7408 section 3.2.2.1: the photoelectric effect
AQA 7408 section 3.2.2.4: wave–particle duality and electron diffraction
hf = φ + Eₖ(max), Eₖ(max) = eVₛ and λ = h/p
Try these tasks
Increase the intensity below threshold and explain why no electrons are emitted.
Compare two above-threshold runs and identify which quantity changes maximum kinetic energy and which changes emission rate.
Find the stopping potential from the photocurrent and explain what is stopped.
Record at least three wavelengths and use the graph gradient to estimate the Planck constant.
Increase the electron accelerating voltage and explain why the diffraction rings become smaller.
Change beam intensity and target structure, then separate brightness effects from geometry effects.