Wed February 27, 2013 By: Animesh Jain

the white light passing through a glass slab must deviate and we should see spectrum but we can't why

Expert Reply
Thu February 28, 2013
Yes the lights does diverge in the glass slab, but when it comes out of the other side of the glass slab, from a face which is parallel to the plane on which the light was incident.
thus they again refract by the same angle and merge forming white light again.
In case of prism, the other face is at different angle to the rays than the first face and hence they dont merge.
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