Surface brightness and radii of the classical cepheids

The dependences between spectral types, colour indices, absolute magnitudes, surface brightness and radii of the stars of luminosity classes I, III and V are presented. The similar comparison is made for the classical cepheids. Their radii Rsub(c) being obtained from surface brightness and absolute magnitudes are compared with the radii R being obtained directly with Wesselink's method. The small but systematic difference log R - log Rsub(c) = +0,06 have been found. (author)