Electromagnetism PHYS20141

Paul.Campbell-3@manchester.ac.uk

Schuster 4-11

PHYS20141 Electromagnetism2

Week 11

- EM waves in the presence of current

- Good conductors and skin depth

- Plasma

- Reflection of EM waves at a perfect conductor

Maxwell’s equations

PHYS20141 Electromagnetism3

Maxwell’s equations in the

presence of current only

PHYS20141 Electromagnetism4

Conductors:

PHYS20141 Electromagnetism5

Skin depth :

Skin depth

PHYS20141 Electromagnetism6

d

Intensity, |E0|2 Intensity, |E0|

2exp[-2z/δ]Conductor, σ

Skin depth

PHYS20141 Electromagnetism7

Plasma

State of matter which is partially ionized and electrons

move under the influence of the electric field –

ignore magnetic field.

PHYS20141 Electromagnetism8

Hence :

Reflection (infinite thickness)

PHYS20141 Electromagnetism9

y

x

y=0

Perfect conductor, E = 0

θI θR

Incident wave, EIReflected wave, ER

PHYS20141 Electromagnetism10

Reflection of EM waves

PHYS20141 Electromagnetism11

Polarization

- Linear polarization

- Circular polarization

- Stokes parameters

Linear polarization

PHYS20141 Electromagnetism12

Circular polarization

PHYS20141 Electromagnetism13

Clockwise rotation (when viewed

from source), “right-handed”

polarization.

Summary of polarization

PHYS20141 Electromagnetism14

Stokes parameters

PHYS20141 Electromagnetism15

Notes on Stokes Parameters

� For a monochromatic plane wave

� Fraction of linear polarization:

� Fraction of circular polarization:

� Alternative forms:

PHYS20141 Electromagnetism16