A light ray enters through a right angled prism at point P with the angle of incidence 30° as shown in the figure. It travels through the prism parallel to its base BC and emerges along the face AC. The refractive index of the prism is:

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Accepted Answer

(4) (√5)/2. Idea: the ray grazes out along AC, so it meets AC at the critical angle c, with sin c=1/μ. The right angle is at A, so r₁+c=A=90° and r₁=90°-c. Snell's law at P: sin 30°=μ sin r₁=μ cos c. μ cos c=μ√1-1/(μ²)=√μ²-1, so 1/2=√μ²-1. μ²=5/4, so μ=(√5)/2.

A light ray enters through a right angled prism at point P with the angle of incidence 30° as shown in the figure. It travels through the prism parallel to its base BC and emerges along the face AC. The refractive index of the prism is:

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