What's the difference between i.e. and e.g.?
(symbol R), fundamental constant of atomic physics that appears in the formulas developed (1890) by the Swedish physicist J. R. Rydberg, describing the wavelengths or frequencies of light in various series of related spectral lines, such as those emitted by hydrogen atoms. The value of this constant is based on the premise that the nucleus of the atom emitting light is exceedingly massive compared with a single orbiting electron (hence the infinity symbol ).