Electron diffraction provides direct evidence that particles have wave-like properties

Quantum Physics - OCR A-Level Physics

Electron diffractionThe diffraction of electrons by a crystal lattice, providing evidence that particles have wave-like properties (de Broglie). provides direct evidence that particles have wave-like properties.
Electrons are accelerated through a potential differenceThe energyThe capacity to do work. Measured in joules (J). transferred per unit chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). between two points. Measured in volts (V). and directed at a thin polycrystalline graphite target.
A pattern of concentric rings is observed on a fluorescent screen, identical in form to the diffraction pattern produced by X-rays through a crystal.
The ring pattern can only be explained if the electrons behave as waves with wavelengthThe minimum distance between two points on a wave that are in phase (e.g. crest to crest). Measured in metres (m). $\lambda = h/p passing through gaps between$ atoms in the crystal lattice.
Increasing the accelerating voltageThe energyThe capacity to do work. Measured in joules (J). transferred per unit chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). between two points. Measured in volts (V). Informal term for potential difference. increases electron speed, which decreases the de Broglie wavelengthThe minimum distance between two points on a wave that are in phase (e.g. crest to crest). Measured in metres (m).The wavelengthThe minimum distance between two points on a wave that are in phase (e.g. crest to crest). Measured in metres (m). associated with a moving particle, demonstrating wave-particle dualityThe concept that all matter and radiation exhibit both wave-like and particle-like properties. Particles have a de Broglie wavelength; photons exhibit particle behaviour in the photoelectric effectThe emission of electrons from a metal surface when electromagnetic radiation of sufficiently high frequencyThe number of complete oscillations passing a point per unit time. Measured in hertz (Hz). is incident on it..., causing the rings to become smaller.
This experiment demonstrates wave-particle dualityThe concept that all matter and radiation exhibit both wave-like and particle-like properties. Particles have a de Broglie wavelengthThe wavelength associated with a moving particle, demonstrating wave-particle dualityThe concept that all matter and radiation exhibit both wave-like and particle-like properties. Particles have a de Broglie wavelength; photons exhibit particle behaviour in the photoelectric effectThe emission of electrons from a metal surface when electromagnetic radiation of sufficiently high frequencyThe number of complete oscillations passing a point per unit time. Measured in hertz (Hz). is incident on it...; photons exhibit particle behaviour in the photoelectric effectThe emission of electrons from a metal surface when electromagnetic radiation of sufficiently high frequencyThe number of complete oscillations passing a point per unit time. Measured in hertz (Hz). is incident on it..: the same electrons that produce the diffraction pattern are detected as individual particles on the screen.

Common Mistake MEDIUM

Students often: Don't say electron diffraction proves electrons are waves.
Instead: Electron diffraction proves electrons exhibit wave-like behaviour. Electrons still behave as particles in other contexts (e.g. they are detected as individual hits on the screen). This is wave-particle duality.