He also did a lot of work on colours and how any colour could be made from just the 3 primaries.
Some, not all, visible colours can be made from just three primaries.
WARNING! Wall of words ahead!
It's complicated, but it you understand the 1931 CIE chromaticity diagram (shown below) it becomes much clearer why any
finite number of so-called primary colors.will
always fail to produce a color gamut that includes
all colors.
The chromaticity diagram
represents all visible colors, with purely spectrum (saturated, monochromatic) colors plotted along its curved outer edge, ranging from deep red with 700nm wavelength to deep violet at 380nm. The straight line connecting 380nm point with 700nm point is often referred to as the purple boundary. All "colors" outside the boundary of this figure are invisible and imaginary to the human eye. There is a third z-axis, not shown here, that completely defines all visible colors in terms of hue and saturation and intensity, but that is not important here. Also, because of color monitor limitations (or printer limitations for hard copy) it is impossible to view an absolutely accurate CIE chromaticity diagram.
The data points that constitute the colored area were empirically derived and averaged from color-matching trials conducted with thousands of volunteer participants. The normal color vision of most of the adult population is represented here. There will be exceptions, people who can see colors outside the boundary at wavelengths shorter than 380nm or longer than 700nm, but this is a very small subset of human population and it is not significant to this discussion. Also excluded are so-called "color blind" people. For everybody else, every possible visible color will occur within the boundary of the graph.
Tristimulus colors are visible colors that can be created by combining three "primary colors" selected from
any colors within the boundary of the graph. This creates a triangle within the CIE graph, with the "primary colors" being at the triangle apexes, and all possible colors that can be produced by mixing various intensities of the "primary colors" occupying the interior area of the triangle. It should be clear by inspection that choosing spectral colors of 380nm (violet), 520nm (green), and 700nm (red) yields a triangle that encloses most, but not all, of the visible colors.
Obtaining saturated spectral light sources was not easy until laser diodes emitting visible wavelengths were invented. A ready supply of blue, green, and red monochromatic light is now available for constructing highly accurate video displays, but most color monitors get by with less than perfection, using three "primary" colors located well within the CIE graph boundary.
I agree with
@WHONOES that the cerebral Scotsman James Clerk Maxwell is virtually unknown to most people, except for those of us who actually use his four equations describing electromagnetic wave propagation. Maxwell's equations completely describe electrical and electronic physics, although we usually use "formulas" derived from those equations for everyday work... Ohm's Law for example. There are many men (and women) of science whose names are virtually unknown, not because they didn't do good work but because they simply did not speak loud enough. Some, such as the Serbian-American Nikola Tesla, spoke perhaps too loud and too long, their legacy buried and ignored until re-discovered late in the twentieth century.
WHY IT IS "PNP" AND "NPN" INSTEAD OF SOMETHING ELSE
Getting back to the point of this thread,
@ratstar is far from being a youngster (see post #23), or even a beginner at electronics experimentation. But his knowledge of semiconductor physics is currently meager at best. There is no denying that semiconductor electronics is complicated and by no means intuitive, or even remotely related to every day experience. Common sense does not apply. The math can sometimes be intimidating. It is worthwhile to try to understand what is going on.
Once anything technical is accomplished, the theoreticians always jump in to try to explain what is occurring. Sometimes they do get it right and suddenly everything becomes clear. Sometimes analogies are useful for visualization, but be very careful in trying to extend an explanation by analogy to encompass situations the analogy does not address. The hydraulic or water flowing under pressure analogy may help to understand electric circuits initially, but water in a pipe is not the same as electrons in a wire. Sometimes existing theory just doesn't provide a useful explanation, but that does not apply to semiconductors, which are understood extremely well as demonstrated by the production of billions, if not trillions, of semiconductor devices each year. The folks that make and sell semiconductor devices
know WTF they are doing.
Any theory may still be incomplete, no matter how accurately it describes reality. Theories are an essential part of the "scientific method" of discovery and explanation. Usually the discovery occurs first and the explanation follows, but this isn't necessary. Black holes were "discovered" as a consequence of Einstein's Theory of General Relativity, but an actual black hole was not "found" until much later in the twentieth century, decades after Einstein. In the center of our own Milky Way Galaxy of all places. Some astronomers now believe that a black hole exists at the center of every galaxy, but there is no way to demonstrate whether that is true.
Just so you know,
@ratstar, just about everyone "in the know" believes bi-polar semiconductor transistors operate the way they do because of two things: electrical field distributions within the semiconductor and the motion of charged entities (holes and electrons) in solids. Holes are somewhat difficult to visualize, since they represent
something that isn't there, namely electrons, but holes exist and move around in a crystal lattice very much like electrons.
In a semiconductor material, such as silicon, holes are created by "doping" the crystal lattice, replacing
just a few of the silicon atoms with atoms that will readily accept an electron. Materials doped in this manner are called "P-type" semiconductors. Doping can also be used to substitute in the crystal lattice a few atoms that will readily give up a free electron. Materials doped in that manner are called "N-type" semiconductors. The nomenclature of "P-type" or "N-type" has nothing at all to do with any applied voltage. The designation of PNP or NPN simply refers to the order in which layers of differently doped material are assembled to form a transistor.