(A Level) Quantum physics

Learning objectives

Describe electromagnetic radiation as a stream of photons, use E = hf = hc/λ with energies in joules and electronvolts, and use p = E/c for the momentum of a photon.

Explain the photoelectric effect with the one-photon-one-electron model, comparing photon energy hf with the work function Φ, and use the threshold frequency and threshold wavelength of a metal.

Use hf = Φ + ½mv²max, and explain why raising the intensity increases the number of photoelectrons (and the current) but not their maximum kinetic energy, which depends only on frequency.

Explain wave–particle duality using the photoelectric effect and diffraction as evidence, describe electron diffraction as evidence that particles behave as waves, and use λ = h/p.

Explain how electrons in an isolated atom can occupy only certain energy levels, and how transitions between them produce emission and absorption line spectra with hf = E₁ − E₂.