I've been trying to understand how polarizing filters work but I have been getting conflicting answers with regards to what direction the polarized light comes out as. On The Physics Classroom, it is said that filters have a polarization axis that is perpendicular to the direction of the filter, which only allows vibrations parallel to the axis through, yet the diagram shows light of the same orientation as the filter passing through:

Filters on light as shown by The Physics Classroom

The book I have been studying says that diagrams often simplify polarization to make the concept easier to understand, but when I'm answering questions such as those about blocking glare with sunglasses, I'm not sure whether or not I should follow the "simplified" version of the diagram, if that statement is even correct.

What orientation is actually correct, or are there different types of filters that achieve both cases?

  • $\begingroup$ You're reading that paragraph incorrectly. It says light perpendicular to the direction of the molecule chains in the filter passes through. Look at the second picture. $\endgroup$ Sep 29, 2018 at 5:54

1 Answer 1


The relevant passage from your link is this

Any vibrations that are perpendicular to the polarization axis are blocked by the filter. Thus, a Polaroid filter with its long-chain molecules aligned horizontally will have a polarization axis aligned vertically. Such a filter will block all horizontal vibrations and allow the vertical vibrations to be transmitted

and to illustrate this I have annotated your diagram as follows

enter image description here

There is a little more about the mechanism here.


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