Ok so not really photography, but here's a little physics phenomenon for you, posted here because well we all have these filters at home to play with. Lets start with a poorly resized image of a computer monitor, and LCD, and something about LCDs is that they have a large linear polariser across their surface: So now to add our camera's linear to circular polariser and adjust the rotation angle so the screen's polariser and our polariser are 90 degrees out of phase: A few notes here: This could be an interesting backlighting project seeing how linear polarised light changes polarisation angle when it scatters off a surface creating the weird backlit effect off my calibrator, ... and all the dust on my screen. And now we add another polariser into the picture. This time a Linear to Circular Polariser, in phase with the screen's linear polariser. This means the light going through the polariser is not cut out, but rather returned to a circular polarisation. The camera polariser has no effect on the circular polarised light beyond it's own insertion loss. Volah if this doesn't get your kids interested in optical physics nothing will... I am serious... this is exactly why there are so few optical physicists in the world.