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Light - Total Internal Reflection - Critical Angle.
1. When a light ray
emerges from glass
into air,
it is refracted and bends
away
from the normal, so i
< r.
2. As i is
made bigger, the refracted
ray
gets closer and closer
to the surface of the glass.
When i equals the critical
angle, the refracted ray
is just touching the glass
surface.
The critical angle
is different for different
materials,
for glass it is about 42
degrees.
Total internal
reflection happens when i is bigger
than the critical angle
(see next
page).
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