6. EM waves in matter with boundaries Flashcards
(25 cards)
How is the frequency of an EM wave affected across a boundary?
It is unchanged by reflection or transmission
How do the incident and reflected angles relate?
They are equal
i=r
What is Snell’s law?
n1sin(i) = n2sin(t)
What are the Fresnel conditions?
n × (H2 − H1) = 0
n × (E2 − E1) = 0
What are the boundary conditions for the s component of an EM wave?
Ei+Er=Et
Hicos(i)+Hrcos(r)=Htcos(t)
What are the boundary conditions for the p component of an EM wave?
Hi-Hr=Ht
Eicos(i)+Ercos(r)=Etcos(t)
What assumption is made for the p component of an EM wave?
The electric field is such that
i=r=t=0
What is the equation for the reflection coefficient for the s component?
rS=Er/Ei
What is the equation for the transmission coefficient for the s component?
tS=Et/Ei
What is the reflectance for the s compinent?
RS=(Er/Ei)2
What is the equation for the reflection coefficient for the p component?
rP=Er/Ei
What is the equation for the transmission coefficient for the p component?
tP=Et/Ei
What are the reflection coefficients at normal incidence for n2>n1?
They are negative
What is the equation for the Brewster angle?
tan(iB)=n2/n1
What is the equation for the Critical angle?
sin(ic)=n2/n1
What is the significance of the Brewster angle?
The Brewster angle is at which the reflection coefficient for the p component is 0
What polarisation is light at the Brewster angle?
S polarised
What is the equation for current density in a conductor?
Jf=gE
Where g is the conductivity
How do B and H relate for isotropic media?
B=µ0µrH
How do D and E relate for isotropic media?
D=ε0εrE
What is the equation for wavenumber for a conductor?
k~sqrt(µgω)
What is the dispersion relation for plane waves?
k2=iµ0µrgω+µ0µrε0εrω2
What is the equation for the skin depth?
δ =sqrt(2/µgω)
What is the wavelength of a wave in a conductor?
λ = 2πδ
Where δ is the skin depth
