E.2.4 (HL)—Particle diffraction

Read the diffraction pattern

A beam of particles can produce diffraction or interference patterns after passing through a suitable crystal or narrow structure. The pattern is evidence that the particles have wave-like behaviour.

Use the experiment as evidence

Electron-diffraction experiments demonstrate wave properties of electrons. This complements the photon evidence from the photoelectric effect: matter and radiation can each show both particle-like and wave-like behaviour.

Connect to wavelength

The wave description is quantified by the de Broglie wavelength $\lambda=h/p$ . A shorter wavelength generally requires a larger momentum.

Common trap

Rutherford alpha scattering is evidence for the nuclear structure of the atom, not the clearest evidence for matter waves. Use particle diffraction or interference when the question asks for wave properties of electrons.

How it is assessed

Questions identify the experiment that demonstrates wave-particle duality or ask what property of electrons a diffraction experiment shows.

Command terms

Identify / State

What earns marks

Name diffraction or interference and explicitly connect it to wave properties of electrons.

Watch for

Choosing line spectra or Rutherford scattering when the question asks for evidence of matter waves.

Retrieve the light model

The photoelectric effect and Compton scattering show photon-like energy and momentum transfer. Threshold frequency and $E_{k,max}=hf-\Phi$ make the photon energy budget explicit.

Retrieve the matter model

Particle diffraction and $\lambda=h/p$ show wave-like matter. For Compton scattering, track energy loss, increased wavelength, and $\Delta\lambda=\frac{h}{m_ec}(1-\cos\theta)$ .

E.2.4 (HL)—Particle diffraction

Interpret Particle Diffraction

E.2.4 (HL) Exam Analysis

Assessment in practice

Retrieve the Quantum Model