Beam penetration method is used inRandom scan systemRaster scan systemBoth a & bNone of these

The Beam Penetration method is used in a Random Scan System.

Here's a step-by-step explanation:

1. The Beam Penetration method is a technique used in computer graphics to display colors.

2. This method is primarily used in random scan systems, also known as vector monitors or calligraphic displays.

3. In a random scan system, the electron beam is directed only to the parts of the screen where a picture is to be drawn.

4. The Beam Penetration method works by varying the penetration of the electron beam into the phosphor.

5. Different colors are produced based on the depth to which the electron beam penetrates the phosphor.

6. Therefore, the Beam Penetration method is not used in raster scan systems, where the electron beam sweeps across the screen in a fixed pattern.

So, the correct answer is "Random scan system".