Polarisers and LCDs
Intermediate
Liquid crystal displays use polarisers.
Liquid-crystal displays place a liquid crystal between crossed polarisers; voltage controls how much it rotates the polarisation, switching pixels on or off.
Phone screens.
Polarised sunglasses can make LCD screens look dark at some angles.
In more detail
Liquid crystal displays use polarisers and liquid crystals that rotate the plane of polarisation, controlling how much light passes through each pixel.
Real-world uses
- Phones, laptops and TVs use LCD screens.
- Sunglasses and filters in cameras use polarisers.
- Phones, laptops and watches use liquid crystal displays, which rotate polarised light to switch pixels on and off.
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Frequently asked questions
How does an LCD create colour?
Colour filters on each pixel select red, green or blue light from the backlight.
Why do LCDs look dark with polarised sunglasses?
Polarisers in the screen and the glasses may be crossed, blocking light.
Why do LCD screens look dark with sunglasses?
The screen emits polarised light in a fixed direction, so some polarised sunglasses can block it at certain angles.
Related topics in Optics
Polarisation of light · Malus's law · Brewster's angle · Birefringence · Optical activity · Coherence and lasers