Picture tube of a television is like the retina of our eyes. They receive video signals and translate them into images. At the back of the picture tube there are three electron guns. This is found in colored television. The three electron guns correspond to three basic colors. They are red, blue and yellow. These colors combine in diverse proportions and create all the other colors that you get to see in a television. The black and white television contains only one electron gun.

The picture tube is coated with phosperous and as the electrons coming with a high speed strikes against the screen, the substance glows and according to the color adjustment system, it obtains the original color of the object that it wishes to display. If the electron beam is strong, then the glow will be brighter, and vice versa. As soon as the electrons beat against the red, green, and blue phosphor dots on the monitor, the dots start glowing. The screen contains holes in it. There is also another substance present over the screen called shadow mask that ensures that the electron beams strike against its own color of the phosphor dots. When all the dots like these start glowing, a complete picture is created.