electromagnetic radiation
[this is a visualisation experiment
designed to discover gaps
in my own intuitions
about light, radio, etc
i hope to revise it
as these gaps are
gradually filled]
everyone's seen video
taken with night-vision goggles
of ghostly green GIs
firing into the dark
these work by detecting
the invisible infrared
radiated by any warm body
and somehow or other
translating it
into visible green light
so we could imagine
a future improvement
where the goggles have
a radio dial
and can be tuned to any frequency
(not just infrared)
displaying radiation of that frequency
as shades of greyscale
and rather than wait
until these 'radio goggles'
are practical/real
we could write a software simulation
that shows more-or-less
what we'd someday see
and by designing this sim
in our imaginations
we can refine our intuitions
without either actual
hardware or software
so one menu we'd want
is 'light sources'
(or radiation sources)
including incandescent bulbs
fluorescent bulbs
neon-etc
LEDs
flames and other chemical reactions
fluorescing chemicals
nuclear reactions (incl the sun)
electric circuits
radio transmitters
etc
and we could start by
choosing one source
and tuning the radio dial
to see how bright
that source shines
at every different frequency
(these graphs are readily available)
another menu would be 'materials'
that can be examined
at different frequencies
and different magnifications
under different light sources
and maybe also 'filters'
that could be inserted between
source and material
not neglecting polarising filters
which the display might indicate
with a different color for each
angle of polarisation
(white for unpolarised)
finally we'd like to include
a realworld mode
where any realworld scene
could be checked out
thru the goggles
toggling back and forth
between natural and 'source' light
with a teaching-menu
of 'textbook scenes'
for each frequency
that include examples to explore
of every interesting phenomenon
at that frequency
now starting with sources
my understanding is
that electromagnetic radiation
always originates from
accelerating or decelerating
electric charges
most often electrons
and that a continuous source
implies oscillating electrons
with the frequency of the oscillation
determining the 'color' of the 'light'
electrons normally bound into molecules
that don't radiate until they're excited
by heat or light or electricity
(while electrons in metals flow freely)
with the color of the radiation, then
depending on the structure of the molecule
probably polarised if
the molecules are aligned
and/or the excitation acts
in a particular direction
so i'd like an overview
of each lightsource in these terms
explaining why it emits
the particular frequencies it does
and special views for
broadcast radio frequencies
(AM and FM)
showing how transmitter-antennas radiate
and why reception is poor
under different conditions
and how 'noisy' electrical circuits
emit radiation unintentionally
and similarly for materials
why does a particular chemical
absorb rather than reflect
(or refract or transmit)
particular frequencies?
and how does it surface texture
influence this?
what happens to its
electron structure
as it absorbs photons?
and how selective absorption
can be used to make
detectors for given frequencies
(including radios and their antennas)
