angle of refraction,ϕ .
For θ < c, $$\delta$$ = ϕ - θ with sinϕ / sinθ = μ or ϕ = sin-1 (μsin θ). ∴ $$\delta$$ = sin-1 (μsin θ) - θ This is a nonlinear relation.
The maximum value of $$\delta$$ is $$\delta$$1 = π/2 - c for θ = c and ϕ = π/2.
For θ > c, $$\delta$$ = π - 2θ $$\delta$$ decreases linearly with θ.
$$\delta$$max = π - 2c = $$\delta$$2 = 2$$\delta$$1.
therefore, $$\delta$$2$$\div$$$$\delta$$1=2.