A prism of angle 75^ and refractive index 3 is coated with thin film of refractive index 1.5 only at the back exit surface. To have total internal reflection at the back exit surface the incident angle must be _ _ _ _ ( 15^ =0.25 and 25^ =0

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A prism of angle 75^ and refractive index 3 is coated with thin film of refractive index 1.5 only at the back exit surface. To have total internal reflection at the back exit surface the incident angle must be _ _ _ _ ( 15^ =0.25 and 25^ =0.43 )

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Correct answer: D. Both (1) & (3)

r₁ + r₂ = 75^ For T I R at back surface 3 r₂ = 3 2 90^ r₂ 60^ r₁ 15^ 1 i = 3 15^ i = 1.73 0.25 i = 0.433 i = 25^ i < 25^

A prism of angle 75^ and refractive index 3 is coated with thin film of refractive index 1.5 only at the back exit surface. To have total internal reflection at the back exit surface the incident angle must be _ _ _ _ ( 15^ =0.25 and 25^ =0.43 )

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