Yesterday I stated (& demonstrated)
Reflection from Metal is Unaffected by a Polarizer
That got me an email asking WHY?
Keep your eye open for the humor or you may miss it
?
The 1st of the images below tells it all (really, I’m not joking)
The 2nd image elaborates
The 3rd image is my view of the 1st two
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Reflection from Metal is Unaffected By a Polarizer
BECAUSE
Light reflected from a non-metallic surface becomes polarized
However – Light reflected from metal is not polarized, due to the electromagnetic nature of light
If light is NOT polarized, then a polarizer has NO effect!
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Here’s the (edited) email.
In your Photographic Improvement lesson, you state that light from metal surfaces is not affected by polarizing filters. I do not see how that can be the case. …. I do not see how reflected light knows what surface reflects it.
The misunderstanding is in the last sentence.
It has nothing to do with what the reflected light knows or doesn’t know.
It has everything to do with the polarizer knowing -
Whether the reflected light is polarized or not
It’s as simple as that 
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These equations (which almost caused me to flunk physics as an engineering student) are known as
Maxwell’s equations - a set of four equations that describe the relations between electricity and magnetism
Q – So what does that have to with light?
A – Light is part of the electromagnetic spectrum, which ranges from radio waves to gamma rays.
Here comes the punch line -
Electromagnetic radiation waves, as their names suggest, are fluctuations of electric and magnetic fields
And that’s where the “Let there be light” joke comes from (just in the off-chance you missed it)
Maxwell’s equations tell all that we need to know to understand light (including how to compute the speed of light – left as an exercise for the interested reader)
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Tune back in tomorrow for our regularly scheduled programming.
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