Discover the Effects of Rotating Polarizing Films | Explained with Examples

[Physics345]

Homework Statement

Imagine that you had two polarizing films and were holding them one on top of the other. what would be the effect of rotating the two polarizing films with respect to one another be? explain what would be seen and why.

Homework Equations

none

The Attempt at a Solution

Let’s say the first polarizer film was in the vertical direction, and the second was in the horizontal direction the light would go through the first vertical polarizer which would polarize the light in that direction, leaving 50% of the light. The remaining 50% vibrating light waves would be negated when they pass through the second polarizer. This would be the same scenario vice versa.

 

[phinds]

Let’s say the first polarizer film was in the vertical direction, and the second was in the horizontal direction the light would go through the first vertical polarizer which would polarize the light in that direction, leaving 50% of the light. The remaining 50% vibrating light waves would be negated when they pass through the second polarizer. This would be the same scenario vice versa.

Uh ... "negated when they pass through the second polarizer"? Don't you mean "they would be blocked when they TRIED to pass through the second polarizer?"

Also, that is just one highly specific case. What happens when you rotate at other angles?

 

[Physics345]

Uh ... "negated when they pass through the second polarizer"? Don't you mean "they would be blocked when they TRIED to pass through the second polarizer?"

Also, that is just one highly specific case. What happens when you rotate at other angles?

My textbook says negated, could it be wrong?
Also what other angles are we referring to?

 

[phinds]

My textbook says negated, could it be wrong?

Negated is not so much the problem as is the statement "they pass through the second polarizer" The point is they do NOT pass through the second polarizer when it is perpendicular to the first.

Also what other angles are we referring to?

ALL other angles

 

[Physics345]

Negated is not so much the problem as is the statement "they pass through the second polarizer" The point is they do NOT pass through the second polarizer when it is perpendicular to the first.
ALL other angles

Why wouldn't they? What exactly is stopping them from passing through the second polarizer?

 

[haruspex]

Why wouldn't they? What exactly is stopping them from passing through the second polarizer?

A polarizing filter effectively poses a question to the photon: are you polarized with me or against me? Simple binary choice. If with me you can go through, if against you can't.
Suppose there are two filters at angle θ. If a photon has got through the first filter it has committed to being polarized in that specific durection. When it has to decide at the second filter, its probability of saying "with" is cos²(θ). Thus, if they are at right angles, its probability of getting through the second filter is zero.

 

[Physics345]

A polarizing filter effectively poses a question to the photon: are you polarized with me or against me? Simple binary choice. If with me you can go through, if against you can't.
Suppose there are two filters at angle θ. If a photon has got through the first filter it has committed to being polarized in that specific durection. When it has to decide at the second filter, its probability of saying "with" is cos²(θ). Thus, if they are at right angles, its probability of getting through the second filter is zero.

Sorry I'm so late with my reply. I re arranged my answer I'm pretty sure I got it now. Have a loo
k
Polarized light; is light whose electric fields are only oscillating in one direction. When un-polarized light whose electric field oscillates in any directions passes through a polarizer, the light becomes polarized. When light passes through the first polarized film, the lights electric field will oscillate in that direction. When they pass through the second polarized film which is perpendicular the remaining electric fields will be blocked, causing there to be no light left at all. Since the two polarized films are rotating perpendicular. Therefore we know regardless of the perpendicular rotation of the two films all light will be blocked off once it reaches the second perpendicular polarized film at all angles.

 

[haruspex]

once it passes through

Except, it doesn't pass through.

 

[Physics345]

Except, it doesn't pass through.

Opps sorry that was a typo I didn't notice that. Other than that, do I have a proper understanding now?
I edited it to "reaches the second polarized film"

 

[haruspex]

un-polarized light whose electric field oscillates in any directions

Make that "many directions" and your answer will be fine.

 

[Physics345]

Done thank you both for your help!