Fourier expansions for the interference film

If the calculation of the squares of the moduli of complex amplitudes is suitably performed in the theory of multiple-beam interference, infinite trigonometric series are obtained, which may be regarded as Fourier expansions of the energy formulae for reflectivity and transmissivity. From this one can directly derive a number of general properties of the interference film of a dielectric, even when metallic coatings are provided at the boundaries.Delivered in the optical section of the 1st Congress of Czechoslovak Physicists, Prague, September 1957.