Loading page description...
Diffraction is the process of waves spreading out as a result of passing through a narrow gap or by a barrier. This process is exhibited by waves, but not by particles, as shown in the diagram. Diffraction can occur in all types of wave and there are a few key examples to know, for example x-rays through metal foil and using a crystal to diffract light. Different experiments and types of waves create different diffraction patterns.
The photoelectric effect is an example of evidence that shows that electromagnetic waves have particle like behaviour. In the photoelectric effect, electromagnetic radiation is fired at a metal foil surface, and as a result electrons are emitted from the foil’s surface. There are no electrons emitted if the energy of the radiation is below the threshold frequency of the metal and above that frequency, the energy of the electrons can range to a maximum kinetic energy. The relationship between the energy of the photon and its frequency is given by the formula in the diagram.
The de Broglie equation links the momentum of the particle to its wavelength. This is related to the theory of wave particle duality, saying that all moving particles act like waves.
End of page