Man's physical universe



theatre demonstrates the path of Hght by the illumination of the smoke

particles which the air contains.

The Reflection of Light Has Some Interesting Modem Applications.

Some objects, such as incandescent lights, are luminous and are

themselves the sources of the light which reaches the eye; but the

majority of objects are visible only

because of the light which they reflect

to the eye.

A perfect mirror would reflect all

of the light falling upon it and would

in itself not be visible, while a rough

surface reflects some of the light and

absorbs some of the light which falls

upon it. The reflected light is reflected

from the rough surface in many directions

and is thus diffused. Under such

conditions the surface becomes visible.

When a ray of light strikes a mirror,

it will be observed that the incident

and reflected rays make the same angle

with a line perpendicular to the mirror

at the point of incidence. This is the

fundamental law of reflection. If two

mirrors are placed at right angles to each

other, the rays will be reflected in a line

parallel to that in which they came,

Fig. 200. The angle of incidence

equals the angle of reflection.

(From Optics and Wheels,

Courtesy of the General Motors


regardless of the angle at which the incident rays reach the first mirror.

If three mirrors are placed perpendicular to each other, as shown in

Fig. 201, all light rays will be reflected back in the direction from

which they came, regardless of how the combination of mirrors is held.

Fig. 201. Reflection from three mirrors at right angles. The entering and

returning rays are parallel, regardless of the position of the mirrors relative to

the direction of the rays.

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