Question

In the derivation of the spherical surface refraction formula, which approximation is applied to the angles made by the incident ray, refracted ray, and normal?

Options

• The paraxial height being large approximation

• The total internal reflection condition

• The small-angle approximation

• The thin-lens approximation

Answer 1

The derivation uses the small-angle approximation for the angles made by the incident ray, refracted ray, and normal. Applying the refraction relation in its small-angle form and rearranging terms in u, v, and R yields the standard formula.