10 Magnetism of Matter 磁 性 Electromagnetic Waves 電磁 波
How can a clay-walled kiln reveal Earth’s
magnetic field of the past?
10-2.7 Find B(r)
R) r
(for
2
) (
2
R) r
(for
2
) (
2
2 0
0
2 0
0 2
0 0 0
0
2 0
0 2
0 0
0 0
dt dE r
B R
dt R dE
E dt R
r d B
dt dE B r
dt r dE
E dt r
r d B
dt s d
d
B E
10-2.8 Displacement Current
0 0 0
0
0 , 0
+
+
E enc
d E
d enc enc
B ds d i
dt i d
dt
B ds i i
10-2.9 Maxwell’s Equati ons
10-3 Electromagnetic Waves
The oscillating E and B Fields
A Most Curious Wave –The ether ( 以太 )
) sin(
) sin(
t kx
B B
t kx
E E
m m
34-3 The Traveling Electromagn etic Wave
hdE
Eh h
dE E
s d E
dt s d
d E
)
(
• The induced electric field:
dt dB dx
dE dt
hdx dB hdE
dt hdx dB
dt hdx d
B B
B
, ), )(
(
hdE
Eh h
dE E
s d E
dt s d
d E
)
(
B c E
t kx
B t
kx kE
t kx
t B B
t kx
x kE E
t B x
E dt
dB dx
dE
m m
m m
m m
) cos(
) cos(
) cos(
) cos(
․The induced magnetic fie ld:
hdB
Bh h
dB B
s d B
dt s d
d
B E
) (
0 0
0 0 0
0 0
0
0 0
0 0 0
0
c 1 1 ,
) /
( 1
) cos(
) cos(
) (
), )(
(
c k
B E
t kx
kx kB
t E t
B dt
hdx dE hdB
dt hdx dE
dt hdx d
E
m m
m E E
10-3.3.1 Radiation Pres sure
) reflection (total
2
) absorption (total
c
p U
c p U
Momentum change
energy change
․The Force Exerted by Radiat ion
) reflection (total
2
2
) absorption (total
c p I
c F IA
c p I
c F IA
c t IA c
p U t
IA t U
F p
r r
GM m c
R P F
F
r
R GM
r
m F GM
cr R P c
R F I
c F IA
r I P
S S
g r
S g S
r S
S r
7 2
3 2
2 2 2
2
10 7
. 16 1
3 3 4
4 4
․The size of comet particles
