If I'm not mistaken polarized light consists of light waves vibrating only in a specific direction because the waves vibrating in other directions have been filtered out. I watched a video on youtube and the guy showed how putting 2 polarizing filters together in a certain alignment so as they block the light altogether. Then he demonstrated something weird he put a third polarizing filter in between the other 2 filters and for some reason this counteracted the opacity of the series of filters so that the final filter actually let light through. The inner and outer filters where at 90 degrees to each other while the middle filter was at 45 degrees. My first guess would be that the filter in the middle changes the vibration plane of the waves that pass through the first filter so that they are no longer blocked by the final filter. (EDIT: Watched that video again and he claims thats how it works) Heres the video What I don't understand is how it works. If I'm not mistaken light consists of waves oscillating in every single one of the 360 degrees but how many of those degrees does the polarizing filter block? I assume if it blocked everything except waves oscillating on 1 specific plane then the 2nd filter would only allow light to pass if it was aligned to the exact same angle of the 1st filter.