Quantum phenomena Flashcards
Photoelectricity
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
Threshold frequency
Minimum frequency of light that can cause photoelectric emission
Wavelength
The distance between two adjacent wave peaks
Work function
Minimum amount of energy needed by an electron to escape from a metal surface
Photon
Packet or ‘quantum’ of electromagnetic waves
Ionisation
Process of creating ions
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
Excitation
Process in which an atom absorbs energy without becoming ionized as a result as a result of an electron inside an atom moving from an inner shell to an outer shell
Ground state
Lowest energy state of an atom
Fluorescence
Glow of light from a substance exposed to ultraviolet radiation; the atoms de-excite in stages and emit visible photons in the process
de Broglie wavelength
The wavelength of a matter particle
de Broglie hypothesis
Matter particles have a wave-like nature characterised by the de Broglie wavelength
De-excitation
Process in which an atom loses energy by photon emission, as a result of an electron inside an atom moving from an outershell to an inner shell
Diffraction
The spreading of waves on passing through a gap or near an edge
Diffraction grating
A plate with many closely-ruled parallel slits
