177.

Let us perform the spectral resolution of the intensity $J$ according to [sect:174.] Sec. 174; namely, $J=\int {𝖨}_{\nu }d\nu .$

Then, by comparison with [eqn:(318)] (318), we find for the intensity of a definite frequency $\nu$ contained in the exciting vibration the value $𝖨=\frac{4\pi }{c}\int {\sin }^2\theta d\Omega ({𝖪}_{\nu }{\cos }^2\psi +{𝖪}_{\nu }^{\prime }{\sin }^2\psi ).\mathrm{\backslash Label}[eqn](320)\text{upshape (320)}$ For radiation which is unpolarized and uniform in all directions we obtain again, in agreement with [eqn:(160)] (160), $𝖨=\frac{32{\pi }^2}{3c}𝖪.$