Re: Which Polarizer?


David Littlewood wrote:
In article <1154792677.076625.165860@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
achilleaslazarides@xxxxxxxxxxx writes

It's fine, provided it is understood that the retardation is
proportional to the thickness of the material. It is, BTW, conventional
to refer to the first of your two directions as the ordinary (O) ray and
the one retarded relative to it as the extraordinary (E) ray. Also, it
might be slightly confusing to say the O ray is "transmitted unchanged".
Both the O and E rays pass through according to the usual laws, but the
refractive index of the material differs in the two directions, so their
velocities are different, and hence their wavelengths are different. The
E ray is slower than the O ray, and thus the two get out of phase.


David,
Thanks, I did not know the terminology for O and E rays. And yes, you
are right, I should not have said "transmitted unchanged", since the
relevant effect of this quarter-wave plate is to introduce a phase
difference between the two components.


But why is it a problem? That light is made of particles is irrelevant
to this, as far as I can see. Could you explain why you think it is?

Well, the question arose as to "coherent" (in-phase) light, and it
seemed that confusion was arising between the phase coherence between
different photons, and the phase coherence of the two orthogonal vector
directions (the "O and E rays") of any given photon. If you weren't
confused, then obviously the clarification was not necessary for you.

However, I do not see the need to discuss photons (in addition to
waves). I guess we all think about these things in different ways,

BTW, I like the idea that "the whole thing can be understood using
nothing but Maxwell's equations". I think if I tried to get my brain to
handle it using nothing but Maxwell's equations (rather than its nice
comfortable little mental pictures) I would struggle.

I meant that the whole thing may be understood using ideas of waves
travelling in space, with no recourse to photons (or any particle
aspects), rather than using only equations. Understanding comes by
analogy, not calculations (and when calculations lead to understanding,
it is through analogy).

.

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