 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 = λ f

 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 μ m.

 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.) I 1 = I 2 B.) I 1 < I 2 C.) I 1 > I 2 D.) There is no current. E.) Not a thing.