PhysicsUK Connections

• 4.5.1(a) Describe the particulate (photon) nature of electromagnetic radiation.
• 4.5.1(b) Define a photon as a quantum of energy of electromagnetic radiation.
• 4.5.1(c) Use E = hf and E = hc / λ to calculate energy of a photon.
• 4.5.1(d) Define the electronvolt (eV) as a unit of energy.
• 4.5.1(e)(i) Use LEDs and eV = hc / λ to estimate the value of Planck’s constant.
• 4.5.1(e)(ii) Determine Planck’s constant using different coloured LEDs experimentally.
• 4.5.2(a)(i) Describe and explain the photoelectric effect and its experimental demonstration.
• 4.5.2(a)(ii) Demonstrate the photoelectric effect using apparatus such as a gold-leaf electroscope and zinc plate.
• 4.5.2(b) Explain that photoelectric emission involves a one-to-one interaction between a photon and a surface electron.
• 4.5.2(c) Use Einstein’s photoelectric equation hf = Φ + KEmax.
• 4.5.2(d) Define work function and threshold frequency.
• 4.5.2(e) State that maximum kinetic energy of photoelectrons is independent of radiation intensity.
• 4.5.2(f) State that rate of emission of photoelectrons above threshold frequency is proportional to radiation intensity.
• 4.5.3(a) Describe and explain electron diffraction as evidence of wave-like behaviour of particles.
• 4.5.3(b) Describe diffraction of electrons through thin polycrystalline graphite and relate to atomic spacing.
• 4.5.3(c) Use the de Broglie equation λ = h / p to relate momentum and wavelength.

H156 v2.0 · May 2026