Page:SahaElectrodynamics.djvu/24

 This equation expresses the law of observation in its most general form. If $$\Phi=\frac{\pi}{2}$$, the equation takes the simple form

We have still to investigate the amplitude of the waves, which occur in these equations. If A and A' be the amplitudes in the stationary and the moving systems (either electrical or magnetic), we have

If $$\Phi=0$$, this reduces to the simple form

From these equations, it appears that for an observer, which moves with the velocity c towards the source of light, the source should appear infinitely intense.

§ 8. Transformation of the Energy of the Rays of Light. Theory of the Radiation-pressure on a perfect mirror.
Since $$\frac{A^{2}}{8\pi}$$ is equal to the energy of light per unit volume, we have to regard $$\frac{A}{8\pi}$$ as the energy of light in