Polarizing Filters

Quick Introduction

Most people are somewhat familiar with polarized filters. We use them in our sunglasses and sometimes on our cameras for special effects. 
Not many have played with filters just for fun. Here are some basics...

This is what happens when you rotate one filter in front of another.

When the angle between the filters is 90 degrees then the light gets blocked.

An interesting thing happens when we have two filters blocking light. We can place a new filter between them which is rotated at 45 degrees.

Notice that the light is no longer blocked entirely. This is counterintuitive.

When we rotate that inserted filter we see that the light is blocked four times per turn. This is because twice it's blocked by filters #1 and #2, and twice by #2 and #3.

We can get some nice effects when we use multiple filters at different angles. A rotating filter will block the light from each sequentially.

This creates a motion effect.

The above illustrations were made using an experimental tool that simulates the behaviour of polarized filters.

It may be useful as an aid to learn about the basics of polarizing filters.
Light intensity I1, I2, I3, etc. can be obtained by hovering anywhere on the canvas.
This can be used to verify calculations by physics students or hobbyists.

Revised 11 Nov 2018