Matter wave
The idea that things long taken to be particles, such as electrons, also behave as waves. Proposed by Louis de Broglie in 1924.
If light is a wave that also behaves like particles, then perhaps particles such as electrons also behave like waves. The French physicist Louis de Broglie argued this in his 1924 doctoral thesis, and showed that the harder a particle moves (the greater its momentum), the shorter its wavelength[1]. The wavelength is Planck's constant divided by the momentum.
The idea gave a reason for the "allowed paths" that had no explanation in Bohr's model: only paths around the nucleus that fit an exact whole number of the electron's wavelengths are allowed.
In 1927 Clinton Davisson and Lester Germer in the United States fired electrons at a nickel crystal and caught the diffraction patterns that only waves can make, confirming that electrons really do behave as waves[2]. Electron waves can be made far shorter than light waves, so they can resolve details that light cannot. The electron microscope relies on this.
Related terms
- DiffractionThe way a wave bends around the edge of an obstacle or spreads out after passing through a narrow gap. Where the waves overlap they reinforce or cancel, producing bright and dark bands.
- Schrödinger equationThe basic equation of quantum mechanics, which governs how the wave of an electron or other particle varies in space and time. Written down by Erwin Schrödinger in 1926.
- Light quantumThe particle-like packet of energy that light behaves as. Now called the photon.