A ray of light incident at an angle $\theta$ on a refracting face of a prism emerges from the other face normally. If the angle of the prism is $5^\circ$ and the prism is made of a material of refractive index 1.5, the angle of incidence is ______.

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A ray of light incident at an angle $\theta$ on a refracting face of a prism emerges from the other face normally. If the angle of the prism is $5^\circ$ and the prism is made of a material of refractive index 1.5, the angle of incidence is 7.$5^\circ$. Explanation: In thin prisms, the distance between the refracting surfaces is ineligible and the angle of prism (A) is very small. Since A = r1 + r2, therefore if A is small then both r1 and r2 are also small, and the same is true for i1 and i2. A = $5^\circ$ μ = 1.5 i2 = $0^\circ$ r2 = $0^\circ$ r1 + r2 = A r1 = A - r2 = 5 – 0 = $5^\circ$ μ = `(sini1)/(sinrlμ) = (sinil)/(sinrl) $\Rightarrow$ sini1 = μsinr1 = 1.5 xx sin $5^\circ$ = 1.5 xx 0.087 = 0.1305 = 7.$5^\circ$ [Solution diagram: 327655_solution_1.png]

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