Conceptual Physics Eight Edition by Paul Gittewitt

This is a very clear introduction to physics. Chapter 26 on Color explains the difference between additive and subtractive color. We have three kinds of color receptors for red, green, and blue which cover the visible spectrum. If we shine lights of these colors in various proportions we can create all the visible colors. If we use physical pigments, then we see red because the pigment reflects red and absorbs green and blue so we can't paint with red, green, and blue to get all colors. Green pigment absorbs red, so using both would be blackish. The colors used in ink are cyan, magenta, and yellow. Cyan absorbs only red, yellow absorbs only blue, and magenta absorbs only green so we use this backwards (subtractive). If we want green we avoid magenta, for red avoid cyan, and for blue avoid yellow. Because light is white composed of all the visible frequencies we need to subtract from it to get the right color when white light is reflected.

Chapter 25 Properties of Light
            An oscillating electric field generates an oscillating magnetic field which in turn generates an oscillating electric field and so on. The vibrating electric and magnetic fields regenerate each other to make up an electromagnetic wave which moves outward from the generating charge. Visible light is a small part of the wave spectrum. The speed of electromagnetic waves must be constant because energy is conserved. If the speed of light slowed the new fields generated would be smaller and smaller with a total energy loss. If light speed increased the energy of the generated field would continue increasing. James Clerk Maxwell found the speed of light from his equations as about 300,000 kilometers per second.