PKG (4) 2" Square Linear Polarized Filter Slide has a 1-3/8” x 15/16” Window.

I bought to do some little tricks for my kids who are learning about light and they show their friends. So great learning tool. Works perfectly for what I wanted.

Perfect for demonstrating the polarization property of light. Place two of these against each other and slowly rotate one relative to the other until the rotation reaches 90 degrees. The light that passes through slowly darkens. When you reach 90 degrees, no light pass through, because between the two filters, light at every polarization angle is blocked.

I expected the direction of polarization to be marked on the slide, but it's not. It's easy enough to figure out, but the oversight seems a little silly to me. If you're getting a number of these, be prepared to check the orientation of each one, as it's unknown whether the manufacturer always does them in the same way. Other than that, they worked fine for my intended use (double-slit experimentation).

These slides are a nice low priced demonstration of Light Polarization for the classroom. They arrived on time and in good condition. The 2 slides can be rotated to show how light decreases as you polarize light in both linear directions.

Some what fragile.Working with the sample piece, use a piece of white glass behind the bottom film then place sample piece on top of bottom film. Place top film in place and look through both films towards a light. You will have to work with the top piece until the films are in correct positions. If you see halos, the glass will not work together..

These are good as a teaching tool and might be useful for some other applications, such as photography. Just be aware that they don't polarize near-infrared or ultraviolet light. (In fact, they don't even polarize violet light very well; if you cross two filters to block light and hold them up to a lamp, you'll see some violet light shine through.)I tried to use these to limit interference between a remote control for my PC and a TV that kept turning off when I used it. The idea was to tape one filter in front of the remote control's infrared LED, another in front of the TV's remote sensor, and rotate the two filters to block the infrared light. But checking with a cell phone camera, I discovered that the infrared light from the remote came right through, no matter how I rotated the filters. Oh, well; nice idea, but no banana....

Lay one on the light, the other on the slide, and Voila! polarized microscopy! Pop in a slide of recrystalized citric acid and start taking pictures of stained-glass artwork made by molecular forces. Rotate one a little and all the colors change. The only way to look at all sorts of bi-refringent stuff. Loads of fun.These are mounted like 35mm projector slides and a little too small for cutting a 32mm filter out, but you can peel apart the cardboard frame, rub off the glue with water, and have a piece of bare polarized film ~49x39mm, use a circle-cutter, and make filters for microscopes and telescopes. Once un-mounted, they do like to curl up a little so you still need a filter frame of some kind but your filter holder is likely good enough.

Product only partially polarizes. I bought 2 pkgs of four filters. All were in definitely USED condition. The are not usable for my purposes which was to include them in a product I am making. Not worth sending back. I do not recommend, not at all.