2.3.45 - Refraction at a boundary

Use n1 sin θ1 = n2 sin θ2 at a boundary between two media and refractive index n = c/v.

Use - refraction at a boundary to connect the rule to the data and decision in the question.

This matters because - refraction at a boundary determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply - refraction at a boundary to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: - Refraction at a boundary is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.