Figure 2-14. Reflection from a plane mirror.

TM 9-258

e. The best reflectors are very smooth metal

2-6.

Law of Reflection

surfaces, some of which may reflect as much as 98

a. The law of reflection is as follows: The angle of

percent of perpendicular light. The glass in a silvered

reflection is equal to the angle of incidence and lies on

mirror serves only as a very smooth supporting surface

the opposite side of the normal; the incident ray,

and protective window for the silver coating on the back.

reflected ray, and normal all lie in the same plane.

In front surface aluminized mirrors, the glass serves only

b. Diagrams A, B, C, and D in figure 2-14 show

as a smooth supporting surface for the aluminum

light rays incident upon plane mirrors at successively

reflecting surface. The resulting aluminum oxide (from

smaller angles. By applying the law of reflection, it can

the oxidation of the aluminum when exposed to the

be seen that in all such cases of reflection the angle of

oxygen in the air) is both colorless and transparent and

reflection can be plotted as long as the angle of

so does not interfere to any appreciable extent with the

incidence is known or vice versa.

passage of light. This type of coating is used on the

reflectors in the huge reflecting astronomical telescopes.

Figure 2-14. Reflection from a plane mirror.

b. Regular reflection occurs when light strikes a

2-7.

Types of Reflection.

smooth surface and is reflected in a concentrated

a. There are two main types of reflection regular

and irregular.

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