Definitions 7: Quantum Physics Flashcards
Photon
A discrete packet of energy of electromagnetic radiation.
Energy of photon = Planck constant x frequency
Photoelectric effect
The emission of electrons when electromagnetic radiation of high enough frequency is incident on a cold metal surface.
Work function (Φ)
Minimum energy needed to remove a loosely-bound electron from the surface of a metal.
Threshold frequency
The minimum frequency of electromagnetic radiation for electrons to be emitted from the metal surface.
Stopping potential
The minimum potential difference between the emitting metal and collector that prevents the most energetic photoelectrons from reaching the collector plate, resulting in zero photoelectric current (in photoelectric experimental set up).
Excitation/de-excitation (of electrons)
A single photon is emitted by an atom when an electron de-excites from a higher energy level to a lower energy level in that atom (likewise when photon is absorbed, electron is excited from lower energy level to higher energy level).
Bremsstrahlung/
Braking radiation
Photons which are produced when charged particles are accelerated or decelerated; bombarding electrons striking metal target experience a distribution of decelerations
De Broglie Wavelength
Wavelength of matter wave that is associated with a moving particle.
Heisenberg Uncertainty Principle
If a measure of position is made with precision Δx and a simultaneous measurement of momentum is made with precision Δp, the produce of the two uncertainties can never be smaller than the Planck’s constant.
