Book 13, Question 115
Why Do Some Screens Go Dark When You Tilt Polarized Glasses?
Polarized lenses only let through light that wiggles in one direction! Many screens already give off light that wiggles one way. If the glasses block that direction, the screen looks black.
More fun facts
- An LCD screen combines a white backlight, a grid of electrodes, a layer of liquid crystals, color filters and two polarizers.
- The rear polarizer polarizes the backlight before it reaches the liquid crystals.
- Voltage from the electrodes turns the liquid crystals, which rotates the direction of the light's polarization.
- Different voltages at each point make black, white and gray dots, and color filters between the polarizers add color.
- The University of Memphis has a demo monitor with its front polarizer removed, so it looks blank until you put on polarized sunglasses.
- Tilting your head while looking at that demo screen makes its colors flip, because the light that was blocked now passes.
Sources: Memphis
Questions kids ask
Will polarized glasses make every screen go dark?
No. It depends on the kind of screen and how its light is polarized.
Is the screen broken when it goes dark?
No. Tilt your head back and the picture returns.