Engineering Physics Annotation << Back PHYSICAL AND METHODOLOGICAL ERRORS IN THE WORKS OF LANDAU F.F. MENDE A phenomenon such as a rainbow is well known. A specialist in electrodynamics is clear that the occurrence of a rainbow is associated with the dependence on the frequency of the phase velocity of electromagnetic waves passing through raindrops. J. Heaviside and R. Wool suggested that such dispersion is associated with the frequency dispersion (frequency dependence) of the dielectric constant of water. Since then, this view is dominant. However, this approach is a physical and methodological error, as shown in this article. Such an error occurred because when recording current in material media, the integral and the derivative of the harmonic function were reversed, which have the same form and differ only in sign. Key words: plasma, dielectric, dielectric constant, dispersion of dielectric constant, harmonic function. DOI: 10.25791/infizik.01.2019.390 Contacts: E-mail: fedormende@gmail.com Pp. 25-33.