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Thus it has changed in the ratio of 1 to $1+{\frac {{\mathfrak {p}}_{s}-{\mathfrak {p}}_{s1}}{V}}$.

If e.g. the rays are falling perpendicular upon a plate, which retreats by the velocity ${\mathfrak {p}}$ in the direction of the perpendicular, then for the incident light ${\mathfrak {p}}_{s}={\mathfrak {p}}$, and for the reflected light ${\mathfrak {p}}_{s1}=-{\mathfrak {p}}$. The variation of the absolute oscillation period during reflection will consequently be determined by the ratio $1+{\frac {2{\mathfrak {p}}}{V}}$.

Also in the ratio between the amplitudes of the incident and the mirrored or refracted light, an influence of Earth's motion can be seen. The amplitude of the dielectric displacement ${\mathfrak {d}}$ is namely with respect to the states of motion considered in §§ 74, 75, 76 and 77

$a,\ a\left(1+{\frac {{\mathfrak {p}}_{s}}{V}}\right),\ a_{1},\ a_{1}\left(1+{\frac {{\mathfrak {p}}_{s1}}{V}}\right)$.

The ratio just mentioned is

${\frac {a_{1}}{a}}$,

in case the earth is at rest, and

${\frac {a_{1}}{a}}\left(1+{\frac {{\mathfrak {p}}_{s1}-{\mathfrak {p}}_{s}}{V}}\right)$,

if it is moving.

In the case previously considered, where the rays are falling perpendicular to the retreating plate, the latter expression becomes

${\frac {a_{1}}{a}}\left(1-{\frac {2{\mathfrak {p}}}{V}}\right)$;

the reflected light will thus be weakened by the motion of the plate. Of course, the opposite motion would strengthen it.

Now the important question emerges, whether these variations of intensity are in accordance with the conservation of energy. To decide this matter, we have to consider, that the aether (due to the motion of light), is acting by certain forces on the mirroring or refracting body