Properties of Matter
The Theme of Technology in Properties of Matter
We've already learned about that funky fourth state of matter: plasma. The word plasma itself has entered our vocabulary with much more frequency thanks to the invention of plasma TVs. Do plasma TVs have anything to do with plasma the state of matter? Yep.
The basic idea of a plasma television is to illuminate tiny colored fluorescent lights to form an image. Each display is made up of millions (sometimes even billions) of pixels, which are just tiny dots on the display. In reality, these pixels are made up of three fluorescent lights: a red light, a green light, and a blue light (RGB for short). By combining these colors in different proportions and intensities, the television screen can produce the entire color spectrum and form our spit the latest reality show or made for TV movie.
Sizes of pixels in different resolutions. (Image from here.)
The plasma display might seem like a newer technology, but it was actually invented way back in 1964 by professors Donald Bitzer and Gene Slottow at the University of Illinois.11 Their first display could only emit green or orange light, but by 1992 the world's first full-color plasma display was ready for its world debut.
One of the main components of a plasma display is plasma. Shocking. We learned earlier that plasma is similar to the gas phase, but the electrons are free to move around positively charge ions of the nucleus. Basically, plasma is a gas with electrons that bounce all over the place.
The inventors of the plasma display realized that under normal conditions a gas is made up of mainly uncharged particles. The individual gas atoms include equal numbers of protons and electrons, making the net charge zero. By tossing in an electrical current (and therefore a bunch of electrons), they could turn a normal gas into a plasma. This explains so much, like why you have to plug in a TV in order for it to work. Eureka.
How do the electrons convert an otherwise normal gas into this weird fourth state of matter? The extra electrons collide with the atoms. This knocks other electrons off of the atom orbitals, further altering the charge balance. The sample of gas has now become a sea of cations and crazy fast electrons. Having charges flying around means we have a plasma.
Xenon and neon atoms are the elements used in most plasma displays. They release light photons when electrons a knocked off of their orbitals. To make a display, hundreds of thousands of tiny cells containing these gases are positioned between two glass plates along with long electrodes on both sides of the cells in a crisscross construction. The entire set-up is insulated with a dielectric material and covered by a magnesium oxide layer which gives an added layer of protection.
The plasma cell construction. (Image from here.)
When an electric current flows through the gas in the cell it releases ultraviolet light particles (called "photons") that interact with the material coated on the inside of the cell which in turn gives off visible light photons. Voilà, we have a picture on a screen that we can see. Magical, right?
Plasma display—not a fancy fish tank. (Image from here.)