Ideal gas except for the specification of these constants. The results of the quantum Boltzmann gas are used in a number of cases including the Sackur–Tetrode equation for the entropy of an ideal gas and the Saha ionization equation for a weakly ionized plasma. The classical thermodynamic properties of an ideal gas can be described by two equations of state: The ideal gas law is the equation of state for an ideal gas, given by: where The ideal gas law is an extension of experimentally discovered gas laws. It can also be derived from microscopic considerations. Real fluids at low density and
Cathode the discharge. Cold cathodes may also emit electrons by photoelectric emission. These are often called "photocathodes" and are used in phototubes used in scientific instruments and image intensifier tubes used in night vision goggles. In a semiconductor diode, the cathode is the N–doped layer of the PN junction with a high density of free electrons due to doping, and an equal density of fixed positive charges, which are the dopants that have been thermally ionized. In the anode, the converse applies: It features a high density of free "holes" and consequently fixed negative dopants which have captured an electron (hence