322
DOC.
11
LECTURE ON ELECTRICITY
&
MAGNETISM
d$x
_
Q
c
dt
H
d%y
_ _
c
öt
d§2
_
dSy
c
dt
e
c
dt
=
0
3x
dx
If
at
one
location
%x
=
&x
=
0
initially,
then
it will also be
so
in
the future
Diagonal
pairs
mutually
independent.
H
85)z
_
d£
y
c
dt
dx
ed£
c
dt
d_&
dx
d
dx
H
d
c
dt
d2&
dx2
eh
d2(&y
_
dt2
=
0
®v =
~
vt)
=
ag(x
-
vt)
v
=
y/ÜM
M
C
~
rr
c
y/e/l
[p. 74]
a
=
/-
In the
case
of
vacuum
v
=
c
%z
=
€y
For
a
dielectric
%z\[ii
=
®y/e",
further
v
=
c
sfzjZ
For
light
waves /i
=
1 v
=
c
=
-
n
=
\[z
holds
for the
majority
of
simple gases
/e
n
and for
some liquids.
In
general, more complicated
relations because the connection
between
JB
and
t
not
so simple.
On the
generation
of electric
waves
later
on.
General differential
equation
of
wave propagation
in
transparent
media
c
dt
dz
fid&z
c
dt dx
d£
uvy
dx
8%
dy
d_
dz
d_
dy