1. The problem statement, all variables and given/known data Suppose light from is moving from water to air. The critical angle be θ i.e. for angle of incidence θ, the angle of refraction is 90°. Refractive index of water wrt air be μ. Suppose the angle of incidence (i) is increased by 1° to θ+1. What happens to the refracted/reflected ray. The angle of refraction (r) would be (?) given by sin r= μ*sin(θ+1). That is if μ =1.33, then θ≈49° say. Then for i= 50°, sin r>1..... not solvable by Snail's law. Due to total internal reflection, r = 90+ (90-50)= 130°. My confusion is, if i is increased from θ by a small amount, will not r also be increased from 90° by a small amount? But due to total internal reflection r is increased by a big amount like 40° ! 2. Relevant equations 3. The attempt at a solution I am not a student. This question is asked by my daughter who is 14 yr old. And I am confused. Please suggest the solution . Thanks.