what does the light bulb do?
It depends on what kind of TV you're talking about. LCDs don't generate any light. For an LCD to be made into a TV or computer display, a light has to be placed behind it. Otherwise, it would look like a calculator display. LCD (Liquid Crystal Display) is a device that alows or prevents light from passing thru it depending on whether electricity is passing thur it or not. Hundreds of thousands of tiny LCDs arranged together make the pictures you see. Older TVs use a CRT which is an electron beam that lights up phosphors inside the screen. This kind of TV gives off light without any light bulb at all. Plasma displays generate light as well and use no light bulb. But there is a light, possible more than one inside an LCD TV that makes it work. They can go bad and rarely do.
There are light projection tv screens. The image is projected on a smaller screen and then you shine a light on the image which is then reflected on to the larger screen (reflective imaging) or the light can pass through the smaller screen which picks up the colors and transfers them to a larger screen (transmissive imaging) which is similar to displaying a movie at a movie theater. Both use a light bulb for projecting the image.
At the rear of the tube is an electron generators, this is modulated by the TV signal, The electron generator projects a high voltage beam negative charged, it passes through a mess which is positive charged in order to separate colors, then to open the beam the surrounding layer of the tube is coated with a conductive metallic charged negatively charged with some thousands volts, the magnetic field of this current sweeps horizontally 640/sec and vertically to opens the beam and projects it over a front phosphorous layer which is luminic reactive to the hitting electrons, this collision leaves photons for a short period of time which is the light we see projected in form of image depending upon the modulation of the reception and amplifying circuitry.
You may be thinking of a projection lamp in a Projection TV. (ie. like a rear screen projection TV set. Instead of using a direct-view setup, like a regular TV set, a projection TV creates a small picture and then uses a beam of light to display that picture at a much larger size. It is that bulb that displays the picture. If the bulb burns out the TV has NO picture.
TV doesn't depend on light bulbs to work. Modern TV's use liquid crystal displays (LCD) and similar technologies. The original televisions used cathode ray tubes (CRT) which has some similarities to incandescent light bulbs: - A CRT works by emitting electrons in a beam, when electricity is applied. The beam hits a plate that glows in response. An electromagnet is used to control the beam, such that a picture is formed on the glowing plate. - An incandescent light works by sending electricity through a thin filament, which also emits a beam of energy, in this case, visible light. Both technologies convert electricity to electromagnetic radiation, but otherwise are completely different.
