Final answer:
To make black using red, green, and blue light, no light should be emitted or reflected, as black is the absence of light. On RGB displays, black is when red, green, and blue are at zero intensity. A red object disappears on a black background with green light because it absorbs the light.
Step-by-step explanation:
To create the color black using red, green, and blue light, no light should be emitted or reflected. This is because black is defined as the absence of light. In the RGB color model used for creating colors on screens and monitors, black is achieved when the red, green, and blue components are all set to their lowest intensity, which is zero. When dealing with illuminated screens, as in the case of televisions and monitors, a display appears black when all the pixels are turned off.
Theoretically, if you were illuminating an object with light and wanted to make it appear black, it would require the absence of any light shining on it. Similarly, a red object would seem to disappear against a black background when illuminated with pure green light because the red object absorbs the green light rather than reflecting any of it, making it indistinguishable from the black background.