phy1020.DVI

Figure 56.1: Addition and subtraction of primary colors.

light; equal proportions of green and blue light make a greenish-blue color calledcyan; and equal proportions
of red and blue light make a purplish color calledmagenta. All three primary colors combined in equal
proportions makewhitelight (Fig. 56.1).
If one of the primary colors is removed from white light, the remaining colors combine to form asec-
ondary colorthat is said to be thecomplementof the missing color. For example, removing the blue light
component from white light leaves yellow light, so yellow is said to be the complement of blue—in a sense,
blue is “anti-yellow” and yellow is “anti-blue”. Similarly, the complement of green is magenta, and the
complement of red is cyan (Table 56-2).
In summary,for lights, the primary colors are red, green, and blue; the secondary colors are cyan, ma-
genta, and yellow.

Table 56-2. Complementary colors.

Color Complement

red cyan

green magenta

blue yellow

These properties of light colors are used in devices we encounter every day. For example, if you enlarge
a color television screen or computer monitor with a magnifying glass, you will see that the image is made
up of an array of small, adjacent red, green, and blue pixels which are combined in different proportions to
form different colors. For example, if you enlarge a part of the screen that contains a yellow image, you will