88.

Wien's displacement law may also in the case of black radiation be stated for the specific intensity of radiation ${𝖪}_{\nu }$ of a plane polarized monochromatic ray. In this form it reads according to [eqn:(24)] (24) ${𝖪}_{\nu }=\frac{{\nu }^3}{c^2}F\left(\frac{T}{\nu }\right).\mathrm{\backslash Label}[eqn](106)\text{upshape (106)}$ If, as is usually done in experimental physics, the radiation intensity is referred to wave lengths $\lambda$ instead of frequencies $\nu$, according to [eqn:(16)] (16), namely ${⋿}_{\lambda }=\frac{c{𝖪}_{\nu }}{{\lambda }^2},$ equation [eqn:(106)] (106) takes the following form: $E_{\lambda }=\frac{c^2}{{\lambda }^5}F\left(\frac{\lambda T}{c}\right).\mathrm{\backslash Label}[eqn](107)\text{upshape (107)}$ This form of Wien's displacement law has usually been the starting-point for an experimental test, the result of which has in all cases been a fairly accurate verification of the law.E.g., F. Paschen, Sitzungsber. d. Akad. d. Wissensch. Berlin, pp. 405 and 959, 1899. O. Lummer und E. Pringsheim, Verhandlungen d. Deutschen physikalischen Gesellschaft 1, pp. 23 and 215, 1899. Annal. d. Physik 6, p. 192, 1901.