There was a time, not so long ago, when all TVs contained a cathode ray tube (CRT) and, as a result, were bulky and heavy. Of course, CRT TV sets still exist and work by firing a stream of negatively charged particles, called electrons, at a phosphor screen. When an electron strikes a phosphor atom, the atom becomes “excited” and emits light of a certain colour, hence creating one picture element, or “pixel”, of a TV picture.
Indeed, the CRT TV dominated the market in the second half of the 20th century, but the search for a thinner, lighter and more energy efficient alternative led to the advent of a raft of TV technologies, most of which are now commonplace.
Plasma TV technology, for example, works on the same basic principle as CRT TV insofar as it relies on excited phosphor atoms to produce each pixel of a TV picture. However, instead of using a CRT, a plasma TV screen lights each pixel with a hot, ionized gas, consisting of atomic nuclei and electrons. This method allows every pixel in the display to be turned on or off at the same time and the absence of a CRT means that plasma TVs can be much thinner and lighter than their CRT counterparts.
A similar comment applies to the competing liquid crystal display (LCD) TV technology, although it’s important to note that LCD panels don’t, by themselves, generate any light of their own. Liquid crystal molecules twist and untwist when a voltage is applied or removed, so they’re simply used to regulate the passage of light from a traditional light source. If light is allowed to pass through a particular pixel, the pixel is “on” and appears light on the TV screen; if not, the pixel is “off” and appears dark.
Another popular TV technology, known as light emitting diode (LED) TV is actually a special case of LCD TV. An LED is a tiny electronic device that emits light when a current passes through it. LEDs can be used to light LCD panels, either by means of an array positioned directly behind the panel or by housing them on the sides of the screen. This leads to what are known as “backlit” and “edge-lit” LED TV screens, but in both cases the screens are, in fact, LCD; the LED only refers to the way in which the screen is lit. Televisions from Argos include plasma, LCD, backlit and edge-lit LED.
