Q71.Marks: +2.0UGC NET Paper 2: Computer Science 11 March 2023
Assertion A: A Raster scan device is a CRT graphic device and can use a television monitor for display
Reason R: In Raster scan display the picture is composed of a series of dots. These dots are traced out as a series of horizontal lines. Television works in a similar fashion.
In the light of the above statements, choose the correct answer from the options given below:
1.Both A and R are true and R is the correct explanation of A✓ Correct
2.Both A and R are true but R is not the correct explanation of A
3.A is true but R is false
4.A is false but R is true
Solution
The correct answer is Both A and R are true and R is the correct explanation of A
Key Points
Statement A: "A Raster scan device is a CRT (Cathode Ray Tube) graphic device and can use a television monitor for display."
This is true since raster scan devices do utilize CRT technology, which is the same technology used in older television monitors. Raster scan devices create images by illuminating individual pixels in a grid (raster), which is similar to the way an old CRT television would display its image.
Statement R: "In Raster scan display the picture is composed of a series of dots. These dots are traced out as a series of horizontal lines. Television works in a similar fashion."
This is also true. When producing an image, a raster scan device does so by drawing out a series of horizontal lines composed of individual dots/pixels--this is also known as scanning. This method of drawing an image is similar to older CRT televisions which produce an image through a similar scan process.
Therefore, as both statements are accurate and Statement R relates directly to the matter raised in Statement A, Both A and R are true and R is the correct explanation of A.
Additional Information
Raster Scan: In raster scan systems, the image is composed of a matrix (grid) of small squares, known as pixels. The electron beam produced by the cathode ray tube (CRT) of the monitor sweeps horizontally from left to right, top to bottom, across the screen. This happens very rapidly - on the order of 60 times per second or more - and each pixel is illuminated when the beam hits it, with the brightness level corresponding to the specific image detail at that pixel. Television monitors and most computer monitors display graphics this way.
Random Scan: In random scan systems (also known as vector graphics or stroke graphics systems), images are drawn by directly specifying the lines that comprise the image, rather than illuminating individual pixels. The picture is stored as a set of line drawings, and the electron beam of the CRT directly draws these lines. This approach is more efficient for images composed mostly of lines, as opposed to complex, filled shapes, which is why it's more common in certain specific applications like oscilloscopes or some CAD systems.
