Crossed Polarizers Black Out an LCD
Image/light can fade nearly to black.
Teaching & key ideas
What you do: Rotate one polarizer while viewing screen/filter stack.
What students see: Image/light can fade nearly to black.
Why it works: Polarizers only transmit one orientation of light; crossed axes block most light.
Question to ask: Why can two clear filters become dark together?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: Why can two clear filters become dark together?