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The
Propagation of Electromagnetic Radiation
-
Radiation
in the sense of "emanates from"
-
An
electric
field surrounds electric charges
-
A magnetic
field surrounds magnets
-
Magnetic
fields make electric charges move
-
Moving
electric charges make magnetic fields
-
Electromagnetic
wave is one big happy party governed by Maxwell's Equations
-
Electromagnetic
waves need matter to start in, but once they get going, they can propagate
through nothing at all (vaccuum)
c
= 3x105 km/s
-
Wavelength
(l=lambda)
determines color of light (see next slide)
-
Since
the speed of light is fixed, you can easily get the frequency, n
of light (how many wave crests pass you each second)
n =
c
/ l
-
We
measure frequency in Hertz (Hz), in honor of Heinrich Hertz who
did early work with radio waves
1
Hz = 1 cycle/s
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