For many people, the most attractive thing about LCD TVs is not the way they make a picture but their flat, compact screen. Unlike an old-style TV, an LCD screen is flat enough to hang on your wall. That's because it generates its picture in an entirely different way.
You probably know that an old-style cathode-ray tube (CRT) television makes a picture using three electron guns. Think of them as three very fast, very precise paintbrushes that dance back and forth, painting a moving image on the back of the screen that you can watch when you sit in front of it.
Flatscreen LCD and plasma screens work in a completely different way. If you sit up close to a flatscreen TV, you'll notice that the picture is made from millions of tiny blocks called pixels (picture elements). Each one of these is effectively a separate red, blue, or green light that can be switched on or off very rapidly to make the moving color picture. The pixels are controlled in completely different ways in plasma and LCD screens. In a plasma screen, each pixel is a tiny fluorescent lamp switched on or off electronically In an LCD television, the pixels are switched on or off electronically using liquid crystals to rotate polarized light. That's not as complex as it sounds! To understand what's going on, first we need to understand what liquid crystals are; then we need to look more closely at light and how it travels.
