DOC.
23
163
observed in the
system
k,
i.e.,
the
energy
of the light
complex
relative
to
the
system
k.
Observed in
the
moving
system,
the
spherical
surface is
an
ellipsoidal
surface
whose equation at
time
r
=
0
is
ßt
-
aß} I
+
V-bßjt
C-
cßy
=
R2
If
S
denotes the volume
of the
sphere
and S'
that of the ellipsoid, then
a
simple
calculation
shows
that
S'
T
v
1
-
J COS if
If
the
energy
of the light enclosed
by
the surface under consideration is
denoted
by
E
when
measured
in the
system
at rest and
by
E'
when
measured
in the
moving
system,
we
obtain
v
K]
111
8i
1
-
Jr
COS if
E
H
8i
1
-
V
V
which
for
p
=
0
reduces
to the
simpler
formula
E
l_
1
-
^
V
E
1
+
^
1
+
V
It is
noteworthy
that
the
energy
and
the
frequency
of
a
light
complex
vary
with the observer's
state
of
motion
according to
the
same
law.
Let
the coordinate
plane
£ =
0
be
a
completely
reflecting surface
at
which
the
plane
waves
considered
in
the last section
are
getting
reflected.
We
ask
for the light
pressure
exerted
on
the
reflecting
surface
and
the direc-
tion,
frequency,
and intensity
of
the
light
after reflection.
[32]
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