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The Total Internal Reflection of Light in Prisms.
A right
angle prism can be used to change the direction
of
a light ray
by 90 degrees or 180 degrees.
A prism can also be used to disperse white light into a spectrum.
How is a Right Angle
Prism used to
Change the Direction
of a Light Ray
by 90 degrees?
A right
angle prism is used to change
the direction of light
by 90
degrees as shown in the picture below.
The light ray enters the prism along
a normal and
continues
straight on until it
hits the back
face of the prism.
Total internal
reflection occurs here
because light strikes the surface at 45
degrees
which is greater than the critical angle.
The light ray then emerges from the prism along a normal
and so continues straight
through the glass surface.
This type of prism can be used in a periscope.
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