Quantum definitions Flashcards
de Broglie hypothesis
matter particles have a wave-like nature characterised by the de Broglie wavelength ( = h/p)
de Broglie wavelength
the wavelength of a matter particle where p is the momentum of the particle
de-excitation
Process in which an atom loses energy by photon emission, as a result of an electron inside an atom moving from an outer shell to an inner shell.
electron volt
Amount of energy equal to 1.6 x 10^-19 J, defined as the work done when an electron is moved through a pd of 1 V.
energy levels
the energy of an electron in an electron shell of an atom
excitation
Process in which an atom absorbs energy without becoming ionised as a result of an electron inside an atom moving from an inner shell to an outer shell.
fluorescence
Glow of light from a substance exposed to ultraviolet radiation; the atoms de-excite in stages and emit visible photons in the process.
ground state
lowest energy state of an atom
ion
An atom that is charged as a result of electrons being added to or removed.
photoelectric effect
Emission of electrons from a metal surface when the surface is illuminated by light of frequency greater than a minimum value known as the threshold frequency.
photon
A packet or ‘quantum’ of light energy.
stopping potential
The minimum potential that needs to be applied to a metal plate to attract all the photoelectrons emitted from its surface back to the surface.
threshold frequency
Minimum frequency of light that can cause electrons to be released from the surface of the metal.
wave – particle duality
matter particles have a wave-like nature as well as a particle-like nature; photons have a particle-like nature as well as a wave-like nature.
work function
minimum amount of energy needed by an electron to escape from a metal surface
