AS AQA Phys Unit 1- Wave-Particle Duality


The dual nature of light

Light is part of the electromagnetic spectrum of waves. Light produces interference and diffraction patterns- alternating bands of dark and light. These can only be explained using waves interfering constructively (when two waves overlap in phase) or interfering destructively (when two waves are out of phase).

The photoelectric effect and particles

Einstein explained the results of photoelectricity experiments by thinking of the beam of light as a series of particle-like photons. If a photon of light is a discrete bundle of energy, then it can interact with an electron one-to-one. All the energy in a photon is given to an electron.


De Broglie initiated the wave-particle duality theory. In his PhD thesis he suggested;

If 'wave-like' light showed particle properties (photons), 'particles' such as electrons should be expected to show wave-like properties.

The de Broglie equation relates a wave property (wavelength) to a moving particle property (momentum, mv) h= Planck's constant 6.63*10^-34 Js;

wavelength = h / mv

The de Broglie wave of a particle can be interpreted as a 'probability wave'.

At the time, de Broglie's ideas were just speculation. However experiments carried out later were able to confirm…


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