What is raster and how is it produced on a picture tube?

Raster refers to a grid of pixels that make up an image, where each pixel represents a specific color or intensity. In a picture tube, such as a cathode ray tube (CRT), raster images are produced by using an electron beam that scans across the screen in horizontal lines from top to bottom. As the beam moves, it activates phosphors on the inside of the screen, creating the visual display by illuminating the corresponding pixels in the raster grid. This process is repeated many times per second to produce continuous images, resulting in smooth motion on the screen.