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Re: POLARIZATION

Donald E. Simanek asked:

... The model of a polarizer as an array of "slits". Where did *that*
model come from?

Hugh Logan responded:

I think this came from the slits between the conductors in the microwave
model and the "slits" between the gold wires ...

I think it came from attempts to understand the rotation of polarizational
planes in crystals. The generic term "optical activity" is often used as a
reference to this phenomenon (see chapter 28 of Jenkins and White). How do
you explain this "rotation" to students? The mechanical model of twisting
"tunnels inside crystals"? Mechanical models of molecules? "Preferences" of
electrons to oscillate along certain directions?

The slit model and the picket fence model fail miserably when applied to
the case of a sandwich of three polarizers. The second's axis is at, say,
45 degrees to the first. The third is at 90 degrees to the first. The
picket fence and slit models would predict no light gets through. But it
does get through.

I am not sure what would happen in such three slits (well lubricated to
minimize friction). Suppose a strong and massive spring is stretched
through the center. In a two slits system (at 90 degrees to each other)
the second slit would act as a reflector of the wave coming from the
first one. But with three slits some oscillations would be transmitted,
more or less according to Malus' law.

And I suspect that the plane of initial polarization (of the wave
traveling along the spring) would be rotated by a sequence of many
"picket fence" slits. Each slit must be twisted at a slightly differnt
angle. I would not be surprized to learn that somebody, perhaps Biot or
Arago, did perform such demonstrations in the first decades of 18th
century. [Most of us associate Biot with magnetic field lines "rotating"
around current wires, not with optical activity of solutions that he
discovered. But in his mind the two investigations were probably
connected.]
Ludwik Kowalski