The principal section of a glass prism is an isosceles triangle PQR with PQ = PR. The face PR is silvered. A ray incident normally on face PQ after two reflections, emerges from the base QR in a direction perpendicular to it. What is the angleQPR of the prism ?

The principal section of a glass prism is an isosceles triangle PQR wi

1.	The principal section of a glass prism is an isosceles triangle PQR with PQ = PR. The face PR is silvered. A ray incident normally on face PQ after two reflections, emerges from the base QR in a direction perpendicular to it. What is the angleQPR of the prism ?
Answer» `36^(@)` `46^(@)` `60^(@)` `72^(@)` SOLUTION : `alpha + 2beta = 180^(@)` and `"" beta = 2ALPHA` HENCE `"" alpha = 36^(@)`.

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The principal section of a glass prism is an isosceles triangle PQR with PQ = PR. The face PR is silvered. A ray incident normally on face PQ after two reflections, emerges from the base QR in a direction perpendicular to it. What is the angleQPR of the prism ?

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