DiagramModerate3 marks
Redraw the diagram given below and complete the path of the light ray AB through the glass prism till it emerges out of the prism. Critical angle of the glass is 42°.
Topic: Total internal reflection in a prism
Question wording verified against source paper
Answer
Solution diagram
Exam answer
Draw the ray entering normally at B, travelling undeviated to the sloping face, undergoing total internal reflection there, and then emerging by refraction from the vertical face.
Explanation
At the sloping face i = 60° > 42°, so total internal reflection occurs. At the next face the angle of incidence is below the critical angle, so the ray emerges.
More from Refraction of Light at Plane Surfaces
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(a) sin 45° / sin 30°
(b) sin 30° / sin 45°
(c) sin 45° / sin 60°
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