



E-field lines originate on positive
charges and terminate on
negative charges (Gauss’ Law)
B-field lines always form closed
loops.
Changing B-field induces an
emf, an E-field (Faraday’s Law).
B-fields are created by moving
charges, currents (Ampere’s
Law).




Electric and Magnetic fields are
interrelated.
Varying E-field with time yields
B-field.
Solution of Maxwell’s Equations
in vacuum yield propagating,
fluctuating, electric and
magnetic fields
Each varying field induces the
other.


Experimentally validated Maxwell’s
EM theories.
First to generate and detect EM
waves in the laboratory.

E-field wave:

High-frequency reversal of the polarity of an electric
dipole creates a varying electric field (time and space).
E
(x,t)

B-field Wave:


Changing polarity of a dipole creates a current.
Changing current induces a varying magnetic field.
B
(x,t)

E-wave Reception: Antenna


E-wave supplies changing E-field at wire  Induces
AC current
B-wave Reception: Loop Antenna

B-wave sets a changing magnetic field through the
wire loop  varying magnetic flux induces a
varying EMF  Induces AC current
c = λf




All bodies emit thermal emission due to movement*
of charges in matter.
The emission spectrum is temperature dependent.
Stars, fire, incandescent light
bulbs, lava, hot coals, etc.
peak in the visible part of the
spectrum.
Humans’ thermal emission
peaks in the infrared, ~12 μm.

EM waves from radio antenna are plane (linearly)
polarized.


Created by charges oscillating in a line.
Thermal emission sources are non-polarized

Created by random thermal motion.

Non-polarized light can be polarized by use of
Polaroid sheets.


Consist of plastic with needle-like crystals oriented
lengthwise
Allow only one orientation of wave to pass
Sheet parallel to polarization passes light unimpeded.
 Sheet perpendicular to polarization reduces flux to 0.




Two perpendicular Polaroid sheets reduces EM flux
to 0.
Polarized sunglasses
3D-movies!

You observe two otherwise identical, thin tungsten
filaments. Filament 1 glows red. Filament 2 glows
yellow/white. What can you say about the respective
currents through the filaments?
A.) I1 = I2
B.) I1 < I2
C.) I1 > I2
D.) There is no current.
E.) Not a thing.