OK, we all can see that those digital projectors used to project PPT, as well as projection TVs, have three beams: blue, green, and red. Also, these three colors are said to be the primary colors of light.
However, violet light is at a higher frequency than blue, so how can a projector mix up to this frequency? It would seem that blue would be top.
For that matter, why can’t mixing be accomplished with red/green/violet? It seems assymetrical: red is at one end of the spectrum, but that which is at the other end–violet–is not included.
Finally, why are 3 beams required? That is, why is the green beam needed? We can’t you just mix between red and blue or red and violet? Why do you need the middle beam?
Thanks for your help. This has really been puzzling me.
I believe those primaries are chosen (as opposed to being something fundamentally natural in physics) simply because of the ways in which our eyes work - in nature, there’s a difference between pure yellow light and a mixture of red and green that we perceive as the same shade.
Some of the answers to your questions are explored in [url=“http://boards.straightdope.com/sdmb/showthread.php?&threadid=144274”]this[/url thread.
Perhaps you have a more complex understanding of projector mechanics than my own, but I’m going off of a kindergarden level explanation of the color wheel. You mix different colors to get an intermediate color, or the appearance of one.
In other words, I don’t think that light from say 560 nm combines with light from 640 nm to make light the color of 600 nm. Your brain combines them so that blue and yellow make green, etc.
But then again, maybe I’m wrong.
Also, isn’t there a red at the upper end of the spectrum as well?