How it Works by Archibald Williams
131. Two rays, A _b_, A _c_, from a point A strike the mirror M at the
255 words | Chapter 36
points _b_ and _c_. Lines _b_ N, _c_ O, drawn from these points
perpendicular to the mirror are called their _normals_. The angles A
_b_ N, A _c_ O are the _angles of incidence_ of rays A _b_, A _c_. The
paths which the rays take after reflection must make angles with _b_ N
and _c_ O respectively equal to A _b_ N, A _c_ O. These are the _angles
of reflection_. If the eye is so situated that the rays enter it as in
our illustration, an image of the point A is seen at the point A^1, in
which the lines D _b_, E _c_ meet when produced backwards.
[Illustration: FIG. 132.]
When the vertical mirror is replaced by a horizontal reflecting surface,
such as a pond (Fig. 132), the same thing happens. The point at which
the ray from the reflection of the spire's tip to the eye appears to
pass through the surface of the water must be so situated that if a line
were drawn perpendicular to it from the surface the angles made by lines
drawn from the real spire tip and from the observer's eye to the base of
the perpendicular would be equal.
[22] Glazebrook, "Light," p. 157.
[23] Glazebrook, "Light," p. 157.
[24] Galileo was severely censured and imprisoned for daring to maintain
that the earth moved round the sun, and revolved on its axis.
[25] For a full account of Animated Pictures the reader might
advantageously consult "The Romance of Modern Invention," pp. 166 foll.
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