Sunlight is often called white light, since it is a combination of all the visible colors. Since the index of refraction is different for each color, the angle of refraction will be different for each color when the light passes from air into glass or other transparent material. This is according to Snell’s Law.
Now if the piece of glass has parallel sides, such as with a window, the light will return in the same direction that it entered the material. But if the material is shaped like a prism, the angles for each color will be exaggerated, and the colors will be displayed as a spectrum of light.
Prism spreading white light into a spectrum of light
The visible colors are in the order of the spectrum. You can remember the order by the name ROY G. BIV. Note that in the illustration above, the colors are distinctly separated. In realty, they blend into each other, such that there are colors in between. For example, there is red-orange in between red and orange…
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