REFLECTION
Before trying to explain reflection, we must first define some important terms shown in Figure 2C.
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Figure 2C
θ
1
θ
2
n
1
n
2
Reflected Ray
Refracted Ray
Angle of Refraction
Angle of Incidence
Incident Ray
Normal
Interface
n
1
is less than n
2
• The normal is an imaginary line perpendicular to
the interface of the two materials.
• The angle of incidence (
θ
1
) is the angle between
the incident ray and the normal.
• The angle of refraction (
θ
2
) is the angle between
the refracted ray and the normal.
Light passing from a lower refractive index to a
higher one is bent toward the normal, as shown in
Figure 2C. Light going from a higher index to a
lower will refract away from the normal, as shown in
Figure 2D-1. As the angle of incidence increases,
the angle of refraction approaches 90
O
to the
normal. The angle of incidence that yields an angle
of refraction of 90
O
to the normal is the critical angle
as shown in Figure 2D-2. If the angle of incidence
increases past the critical angle, the light is totally
reflected back to the first material so that it does not
enter the second material as shown in Figure 2D-3.
The angles of incidence and reflection are equal.
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The above paragraphs are reproduced by permission TECHNICIAN’S GUIDE TO FIBER OPTICS 2E (PAGE 39)
By Donald J Sterling, Jr. - DELMAR PUBLISHERS, INC., Albany, New York, Copyright 1993
