Question
Sat January 28, 2012 By:
 

Mathematically prove that when a light ray passes through a rectangular glass slab, the incident ray is parallel to the emergent ray. Illustrate with a diagram.

Expert Reply
Mon January 30, 2012
In triangle GBC,
r1+90-r2=90
so r1=r2
as ?=sin i/sin r1 =sin r2/sin e    as r1=r2
so i=e
so for, CF and DE, and intercector CD
angle BCF=angle CDE=corresponding angle
so CF parallel to DE.
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