According to the usual explanation, polarized lenses work by only allowing light with a specific kind of polarization. It’s a simple explanation, and makes a lot of sense.
Why is it then, than when I look at a screen with two polarized glasses, one at an angle from the other, the image does not dim in the overlapping region, when it does in the glass closer to my eyes?
In: 3
Think of waves of light kind of like pieces of paper. They are very thin, basically infinitely thin, but they do vibrate in a plane which makes them wide.
If you have a bunch of vertical slits and you throw a bunch of random pieces of paper at those vertical slits, at least a few of them will happen to be upright and will be able to slide through. But if you place a bunch of horizontal slits right behind those vertical slits, then suddenly there is just a bunch of little holes and no real width to them. So none of the pieces of paper will be able to slide through at all.
ELI5 would probably delete this answer but I think one or both of your polarizer lens is fake.
It depends on the type of polarization. Sunglasses, for instance, would probably have both lenses polarized against the same type of light; once you filter out the light, filtering it the same way won’t have any obvious difference. It’s like picking out all of the red candies, and then picking out all the red candies again; unless more red candy was added in between, the second filter won’t change anything.
Meanwhile, 3D glasses that use polarization will have different types used in each lens (so that the differently polarized frames are only visible to the appropriate eye). Looking through both lenses at once (such as using a mirror if you don’t want to take the lenses out of their frame) will have a dramatic darkening where they overlap.
If two polarised lens don’t block light when u rotate them, then one or both are not properly polarised. You can do this as a quick test when buying polarised Sunny’s at a store, test two of the same pair and rotate one pair and if the lens don’t fully black out, then you’re getting scammed
The screen itself has a polarised filter so you are encountering the three-filter paradox. It’s a quantum mechanical effect: https://youtu.be/zcqZHYo7ONs
In a nutshell:
The photons do not have an underlying “true” polarity. If they did, you would rightfully expect holding your second pair of glasses at 45 degrees to cancel *more* light than just your one pair of glasses.
Instead, the photons have a *probability* to cross each polarizing filter, depending on the orientation of the last polarization they went through. When passing from the screen (polarized one way) through your one pair of glasses (polarized the other way) the photons have a very low probability of crossing. However, when you introduce another filter at 45 degrees there’s a much higher likelihood that the polarized light from the screen will pass through it AND there’s a higher likelihood that the light from the 45 degree filter will pass through your first pair of glasses.
This adds up so that filter A, B, and C let through more light together than if you just had A and C.
Adding more filters turned incrementally between one another will effectively cancel out the polarization effect. Essentially, each filter serves as a rung on a ladder or a step on a staircase – going from the bottom directly to the top is almost impossible, but if you have a step in the middle it becomes much easier to get up.
Yes, this is very counter-intuitive – like a lot of quantum phenomena.
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