UGC NET CSE | June 2014 | Part 3 | Question: 01

Question

Beam-penetration and shadow-mask are the two basic techniques for producing color displays with a CRT. Which of the following is not true ?

I. The beam-penetration is used with random scan monitors.

II. Shadow-mask is used in rasterscan systems.

III. Beam-penetration method is better than shadow-mask method.

IV. Shadow-mask method is better than beam-penetration method. 

• A. I and II 
• B. II and III 
• C. III only
• D. IV only 

Answer 1

Ans should be C           

Two main methods for producing color in CRT Monitors are:
1. Beam Penetration Method
2. Shadow-Mask Method

Difference between Beam Penetration and Shadow Mask method.

	Beam Penetration method	Shadow Mask method
Where Used	It is used with Random Scan System to display color.	It is Used With Raster Scan System to display color.
Colors	It can displays Only four colors i.e. Red , Green, Orange and Yellow.	it can display Millions of colors.
Color Dependency	Less colors are available because the colors in Beam Penetration depends on the speed of the electron beam.	Millions of colors are available because the colors in Shadow Mask depends on the type of the ray.
Cost	It is Less Expensive as compared to Shadow Mask.	It is More Expensive than other methods.
Picture Quality	Quality of  picture is not so good i.e. Poor with Beam Penetration Method.	Shadow Mask gives realism in picture with shadow effect and millions of color.
Resolution	It gives High Resolution.	It gives Low Resolution.
Criteria	In Beam Penetration method, Color display depends on how far electron excites outer Red layer and then Green layer.	In Shadow Mask Method, there are no such criteria for producing colors. It is used in computers, in color TV etc.

 

Comments

Now, unlike the beam penetration CRTs where the acceleration of the electron beam was being monitored, we now manipulate the intensity of the 3 beams simultaneously. If the red beam is made more intense, we get more of red color in the final combination etc. Since fine-tuning of the beam intensities is comparatively simple, we can get much more combination of colors than the beam penetration case. In fact, one can have a matrix of combinations to produce a wide variety of colors.

The shadow mask CRT, though better than the beam penetration CRT in performance, is not without it's disadvantages. Since three beams are to be focused, the role of the "Shadow mask" becomes critical. If the focusing is not achieved properly, the results tend to be poor. Also, since instead of one pixel point in a monochrome CRT now each pixel is made up of 3 points (for 3 colors), the resolution of the CRT (no. of pixels) for a given screen size reduces.

http://ecomputernotes.com/computer-graphics/graphics-device/what-is-color-crt-display-explain-beam-penetration-and-shadow-mask-method

please correct me if I am wrong, In my opinion Shadow mask is better ans must A

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question is about which one is not true