DOC.
23
165
The
energy (measured
in the
system
at
rest)
striking the unit surface
of
the
mirror
per
unit time is
obviously
A2/8i(V
cos

v).
The energy leaving
the unit surface
of
the
mirror
per
unit time is
A'"2/8j(Vcos
p'" +
a).
According
to
the
energy
principle, the difference of these
two expressions
is
the
work
done
by
the light
pressure per
unit time.
Equating
this
work
with
P.v, where
P
is the
pressure
of
light,
we
obtain
COS
(p
V
P
=
2
V
Si
V
1
V
In first
approximation,
in
agreement
with
experience and
with other theories,
we
get
P

2
COS2
Kß .
All
problems
in
the
optics
of
moving
bodies
can
be solved
by
the
method
employed
here.
The
essential
point
is that the
electric
and
magnetic
forces
of light,
which
is influenced
by a moving
body,
are
transformed
to
a
coordi
nate
system
that is
at rest
relative
to
that
body.
This reduces
every problem
in
the
optics
of
moving
bodies
to
a
series of
problems
in
the optics
of
bodies
at
rest.
$9.
Transformation
of
the MaxwellHertz
equations
when
convection
currents
are
taken
into consideration
We
start from
the
equations
7
{V
+
fl
_
Ty
dN
Tz
dH
'
1
V
It
dl
~
dY
dZ
Tz
~
ly
yp
+
ft
=
Tz dl
~
Hi dN
'
1
SM
dZ
dX
Vit
~
Ix
Tz
_
dm
_
dl
1
8N dX dY
~8y
'
lit
= ly
Ix
[34]
[35]