Wave per unit distance (typically per meter), can be associated with the wavelength by the relation The period formula_33 is the time for one complete cycle of an oscillation of a wave. The frequency formula_34 is the number of periods per unit time (per second) and is typically measured in hertz denoted as Hz. These are related by: In other words, the frequency and period of a wave are reciprocals. The angular frequency formula_28 represents the frequency in radians per second. It is related to the frequency or period by The wavelength formula_30 of a sinusoidal waveform traveling at constant speed
Madelung constant Madelung constant allows for the calculation of the electric potential "V" of all ions of the lattice felt by the ion at position "r" where "r" =|"r" - "r"| is the distance between the "i"th and the "j"th ion. In addition, If the distances "r" are normalized to the nearest neighbor distance "r" the potential may be written with formula_3 being the (dimensionless) Madelung constant of the "i"th ion The electrostatic energy of the ion at site formula_5 then is the product of its charge with the potential acting at its site There occur as many Madelung constants formula_3 in