Quantum Mechanics demystified, a try
Most people know about polarized sunglasses, how one can see more clearly with them in certain glaring situations. Also people might know on high level how polarization works, by passing through light (photons) with waves vibrating only to one direction. Having two perpendicularly polarizing films one after each other, no photons will pass through. Etc.
Why am I talking about this?
I am trying to understand the nature of light and specifically how/why interference patterns are created in double slit experiments. Even more precisely, why does interference patterns vanish once an observation is made to detect through which slit the photon is traveling.
One of the methods used to observe is to use polarizing film. What happens in polarization such that it makes interference vanish?
Light is a bunch of photons propagating in space as a electromagnetic wave, a disturbance in the electric (and magnetic) field.
Electric field being a dipole field, each through and crest of disturbing force is fluctuating between maximum and minimum values in one linear direction. That’s the polarization!
If consecutive through-crests (‘~photons~’) have the same polarisation, we have a linearly polarized wave. We talk about p-polarized wave, if the polarization is along a plane we are interested in, or a s-polarisation in perpendicular case. Polarization can also be rotating, in which case consecutive through-crest’s forces come in different angles. Normally angles are varying in some regular way, like circular or elliptic.
Polarity is created by the source of the wave, like vibrarting electrons, thermal radiation or annihilating particle-antiparticles. Most often these sources are regular in nature, producing reqularly or steadily polarized radiation.
What makes material polarizing then, like in polarizing film?
One way is to use parallel aligned long-chained polymers. This material let’s photons polarized along the chains pass freely through but prohibiting other polarizations, perpendicularly polarized ones in full.
But why is that?
One candidate is $C_2H_3Cl$. Two Carbons are linked with double covalent bond, other Carbon has two Hydrogens with single covalent bond and the other one Hydrogen and one Chlorid both with single covalent bonds:
H H
\ /
c = C
/ \
Cl H
These monomer molecules are chained into polymer chains by replacing the double covalent bond between Carbons with a single one and letting the other electron participate in single covalent bonding with adjacent monomer:
H H H H H H H H
| | | | | | | |
. . . - C - C - C - C - C - C - C - C - . . .
| | | | | | | |
Cl H Cl H Cl H Cl H
Chained polymers are then joined to each other in parallel with Van Der Waals
In resulting structure, highly reactive electrons, most likely ones on Cl outer orbital, are positioned topologically in such a manner that they are only reacting with photons with polarity non-aligned to direction of the polymer chain. They do not interact with photons of polarity aligned with the chains. Chains are kind of resonating only to non-aligned vibrations, letting aligned ones pass through.