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Powerpoint Templates
Electromagnetic
Radiation
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1887 (22 years after Maxwell equations) discovered radio waves
Hertz(1857-1894)
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Maxwell Equations
β.π·= π
β.π΅= 0
βπ₯π»= π½+ ππ·ππ‘
βπ₯πΈ= β ππ΅ππ‘
πΉ= π(πΈ+ π£Τ¦ π₯ π΅)
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πΉ= π(πΈ+ π£Τ¦ π₯ π΅)
1.
2
.
kineticE m v v
dE d vm v F v
dt dt
. [ . .( )]dE
F v q E v v v x Bdt
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Constitutive Equations
Vacuum
D = Ξ΅o E
B = ΞΌo H
Conductors
J = Ο E
Linear media
D = Ξ΅ E
B = ΞΌ H
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Non linear media
P = Ο(1)E + Ο(2)E2 + Ο(3)E3 + β¦
D = Ξ΅o(E + Ο(1)E + Ο(2)E2 + Ο(3)E3 + β¦)
D = Ξ΅o(E + P)
βπ₯π»= π½+ ππ ππΈππ‘ + ππ ππππ‘
βπ₯π»= π½+ ππ·ππ‘
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Example SHG
E = πΈπππππ‘
π= πΈ2 = πΈπ2ππ2ππ‘
βπ₯π»= π½+ ππ ππΈππ‘ + ππ ππππ‘
βπ₯πΈ= βπ ππ»ππ‘
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Gauss Theorem
β.π·= π
ΰΆ± β.π·V ππ= π·.πα¬Τ¦ ππππ = π
Isotropic media => Spherical field
4Οr2π·= π => πΈ= 14πππππ2
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ΰΆ± β.π΅V ππ= π΅.πα¬Τ¦ ππππ = 0
β.π΅= 0
NΒΊ of field lines entering a volume must be equal
to the nΒΊ of lines living the volume (no magnetic
charge accumulation allowed). => Field lines are
closed loops.
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Stokes Theorem
ΰΆ± βπ₯π»S .ππ= ΰΆ» π».ππππ
ΰΆ± ( π½+ ππ·ππ‘S ).ππ= ΰΆ» π».ππππ
I = 2πππ» => π΅= 12πππΌπ
DC current
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Free Space
β.πΈ= 0
β.π΅= 0
βπ₯π΅= ππππ ππΈππ‘ = 1π2 ππΈππ‘
βπ₯πΈ= β ππ΅ππ‘
βπ₯βπ₯πΈ= β βπ₯ππ΅ππ‘ = β πππ‘(βπ₯π΅)
βπ₯βπ₯πΈ= β(β.E) β β2πΈ
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β2πΈ= 1π2 π2πΈππ‘2
β2π΅= 1π2 π2π΅ππ‘2
Possible solution: Plane waves
E= Eocos (kα¬Τ¦.r α¬α¬Τ¦β Οt + β )
B= Bocos (kα¬Τ¦.r α¬α¬Τ¦β Οt + β )
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β.πΈ= 0 β.π΅= 0
E= Eocos (kα¬Τ¦.r α¬α¬Τ¦β Οt + β )
β.πΈ= ΰ΅«β.πΈπ + πΈo.πα¬Τ¦ΰ΅―cosΰ΅«kα¬Τ¦.r α¬α¬Τ¦β Οt+ β ΰ΅―
B= Bocos (kα¬Τ¦.r α¬α¬Τ¦β Οt + β )
πα¬Τ¦.πΈo = 0 πα¬Τ¦.π΅o = 0 πα¬Τ¦π₯πΈo = ππ΅π
πα¬Τ¦π₯π΅o = β ππ2 πΈπ
Θ<πΈΘ<Θ<π΅Θ<= π
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Potentialsπ΅= βπ₯π΄
πΈ= ββπβ ππ΄ππ‘
β.π΄+ 1π2 ππππ‘ = 0
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Law of reflection: ΞΈi = ΞΈr
Snellβs law: n1 sin ΞΈi = n2 sin ΞΈt
R
2
2
( )
( )i t
i t
tgR
tg
2
2
( )
( )i t
i t
sinR
sin
2 2
(2 ) (2 )
( ) ( )i t
i t i t
sin sinT
sin cos
2
(2 ) (2 )
( )i t
i r
sin sinT
sin
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Brewster's angle: 56.4ΒΊ
Total reflection: 42ΒΊ