| The most common computer monitors are 2 types. | | | | transparent polarising sheets. The polarizing axes of |
| The most common is the cathode ray tube. It is the | | | | the two sheets are aligned perpendicular to each |
| type you are probably most familiar it is also the oldest | | | | other. Each cell is supplied with electrical contacts that |
| design typecathode-ray tubeelectron tube in which | | | | allow an electric field to be applied to the liquid inside. |
| electrons are accelerated by high-voltage anodes, | | | | Before an electric field is applied, the long, thin |
| formed into a beam by focusing electrodes, and | | | | molecules in the liquid are in a relaxed state. Ridges in |
| projected toward a phosphorescent screen that | | | | the top and bottom sheet encourage polarization of |
| forms one face of the tube. The beam of electrons | | | | the molecules parallel to the light polarisation direction |
| leaves a bright spot wherever it strikes the phosphor | | | | of the sheets. Between the sheets, the polarization of |
| screen. To form a display, or image, on the screen, the | | | | the molecules twists naturally between the two |
| electron beam is deflected in the vertical and horizontal | | | | perpendicular extremes. Light is polarized by one sheet, |
| directions either by the electrostatic effect of | | | | rotated through the smooth twisting of the crystal |
| electrodes within the tube or by magnetic fields | | | | molecules, then passes through the second sheet. The |
| produced by coils located around the neck of the tube. | | | | whole assembly looks nearly transparent. A slight |
| Some cathode-ray tubes can produce multiple beams | | | | darkening will be evident because of light losses in the |
| of electrons and have phosphor screens that are | | | | original polarizing sheet. |
| capable of displaying more than one color. | | | | When an electric field is applied, the molecules in the |
| Cathode-ray tubes are used in television sets, | | | | liquid align themselves with the field, inhibiting rotation of |
| computers, automated teller machines, oscilloscopes, | | | | the polarized light. As the light hits the polarizing sheet |
| and radar displays This is the type of monitor that you | | | | perpendicular to the direction of polarization, all the light |
| are most familiar with. | | | | is absorbed and the cell appears dark. |
| The newer type is called liquid crystal display A liquid | | | | The newer type has native resolution this means you |
| crystal display, or LCD, is a thin, lightweight display | | | | cant change the dot pitch or the resolution like you can |
| device. It consists of an electrically-controlled | | | | with the cathode ray tube or older type. |
| light-polarizing liquid trapped in cells between two | | | | |