Let the refractive index of the rectangular slab be μ ≥ √2.
μ = 1/sin ic
sin ic > 1/ μ
cos r ≥ 1/ μ
sin i/sin r = μ
From Snell’s law
Sin I = μ sin r
i = 90o
1 + 1 ≤ μ2
2 ≤ μ2
Taking the square root
√2 ≤ μ
Let the refractive index of the rectangular slab be μ ≥ √2.
μ = 1/sin ic
sin ic > 1/ μ
cos r ≥ 1/ μ
sin i/sin r = μ
From Snell’s law
Sin I = μ sin r
i = 90o
1 + 1 ≤ μ2
2 ≤ μ2
Taking the square root
√2 ≤ μ