What is meant by wave-particle duality?

Wave-particle duality is the idea that electromagnetic radiation and matter each show wave behaviour in some experiments and particle behaviour in others, and that a complete description needs both models.

Name three properties of light that are explained by the wave model.

Diffraction, interference and polarisation are all explained by the wave model and cannot be explained by treating light as a stream of particles.

Name two effects that require the photon model rather than the wave model.

The photoelectric effect and the production of line spectra both require the photon model, because each depends on radiation delivering its energy in discrete amounts.

Name two behaviours of light that can be explained by either model.

Reflection at a plane surface and refraction at a boundary can both be described successfully by the wave model or by the photon model.

Is the formation of a diffraction grating pattern explained by the wave model, the photon model or both?

By the wave model, because the sharp beams arise from the superposition of waves from many slits arriving in phase.

Is the photoelectric effect explained by the wave model, the photon model or both?

By the photon model only, because the threshold frequency and the instant emission cannot be reconciled with energy arriving as a continuous wave.

CCEA A-Level Physics 1210

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Wave-Particle Duality

Wave model, photon model and both

2 things to know
Unit AS 2

Overview

Recall questions on what wave-particle duality means, which properties of light the wave model explains, which effects need the photon model, which are explained by either, and the case-by-case classification of diffraction, the photoelectric effect, Young's fringes, line spectra, polarisation and reflection.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Explain the statement that light travels as a wave but interacts as a particle.

Key term

Give one observation that could never be explained by treating light purely as a stream of particles.

Questions from this subtopic

Each one with the model answer underneath.

1
What is meant by wave-particle duality?
Model answer
Wave-particle duality is the idea that electromagnetic radiation and matter each show wave behaviour in some experiments and particle behaviour in others, and that a complete description needs both models.
2
Name three properties of light that are explained by the wave model.
Model answer
Diffraction, interference and polarisation are all explained by the wave model and cannot be explained by treating light as a stream of particles.
3
Name two effects that require the photon model rather than the wave model.
Model answer
The photoelectric effect and the production of line spectra both require the photon model, because each depends on radiation delivering its energy in discrete amounts.
4
Name two behaviours of light that can be explained by either model.
Model answer
Reflection at a plane surface and refraction at a boundary can both be described successfully by the wave model or by the photon model.
5
Is the formation of a diffraction grating pattern explained by the wave model, the photon model or both?
Model answer
By the wave model, because the sharp beams arise from the superposition of waves from many slits arriving in phase.
6
Is the photoelectric effect explained by the wave model, the photon model or both?
Model answer
By the photon model only, because the threshold frequency and the instant emission cannot be reconciled with energy arriving as a continuous wave.

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