CRTs and LCDs

The screen of a computer is often known as the monitor, or VDU (visual display unit). Inside the computer, there is a video card which processes images and sends signals to the monitor.

When choosing a monitor, you have to take into account a few basics.

Type of display - the choice is between a CRT or an LCD screen.

The Cathode Ray Tube of a monitor is similar to a traditional TV set. It has three electron guns (one for each primary colour: red, green and blue) that strike the inside of the screen, which is coated with substances called phosphors, which glow and create colours. CRTs are cheap, but they are heavy, can flicker and emit radiation.

A Liquid Crystal Display is made from flat plates with a liquid crystal solution between them. The crystals block the light in different quantities to create the image. Active-matrix LCDs use TFT (thin film transistor) technology, in which each pixel has its own transistor switch. They offer better quality and take up less space, so they are replacing CRTs.

Screen size - the viewing area is measured diagonally: in other words, a 17 screen measures 17 inches from the top left corner to the bottom right.

Resolution - the clarity of the image depends on the number of pixels (short for picture elements) contained on a display, horizontally and vertically. A typical resolution is 1,024 x 768. The sharpness of images is affected by dot pitch, the distance between the pixels on the screen, so a dot pitch of 0.28 mm or less will produce a sharp image.

Brightness - the luminance of images is measured in cd/m- (candela per square metre).

Colour depth - the number of colours a monitor can display.

Refresh rate - the number of times that the image is drawn each second. If a monitor has a refresh rate of 75 Hertz (Hz), it means that the screen is scanned 75 times per second. If this rate is low, you will notice a flicker, which can cause eye fatigue.

(from Professional English in use)

17. Find English equivalents in the text:

Електронно-променева трубка, електронна гармата, вдаряти, випромінювати радіацію, рідинний розчин, кількість, транзисторний перемикач, різкість зображення, частота оновлення, крок розташування точок, яскравість, миготіння, втома очей.

18. Match each term with the appropriate definition:

1. phosphors	a) the frequency at which a monitor renews its image, measured in Hz
2. LCD screen	b) a flat-panel display which works by emitting light through a special liquid
3. pixel	c) the space between a display's pixels
4. dot pitch	d) the smallest element in a displayed image
5. refresh rate	e) materials that emit light and produce colours when they are activated by an electron beam
6. resolution	f) the viewing area is measured diagonally
7. thin film transistor	g) the quality of being sharp and clear
8. screen size	h) is a special kind of field-effect transistormade by depositing thin films of a semiconductor active layer as well as the dielectric layer and metallic contacts over a supporting substrate
9. sharpness	i) the derived SI unit of frequency
10. Hertz	j) the clarity of the image depends on the number of pixels contained on a display, horizontally and vertically

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