I saw a video where they used polarizing filters. At first they took two and put them so that one is perpendicular to the other. They shone light through them and nothing passed. They then inserted a third filter in between, at 45 degree angle, and some light passed through. They claimed this shows how weird quantum mechanics is since there is no classic explanation as to how a filter increases light.
Now, I understand the explanation of quantum mechanics. But why can't it be explained classically (without collapsing and probabilities)? If I understand correctly, we can think of a filter as projecting the light wave onto its axis. So the horizontal filter will take the y portion of the wave, and the vertical filter will take the x portion. If placed on on top the other, then after the wave passes the first, it has no component of the axis of the second filter, so nothing passes through. But, if we insert a 45 angle filter in between, then it'll project the wave to its axis and then the wave has a portion that can be projected to the third filter's axis. It's thinking of filters as slits that cause the wave to align as it passes through them.
The amount of light that passes will be different in the two theories (I think 1/8 in quantum and ~1/2 in my classic explanation (if it is correct)), but the fact that inserting a filter causes light to pass through can be explained in both cases, no?
UPDATE: The video is https://www.youtube.com/watch?v=zcqZHYo7ONs&vl=en