Read Prism TIR: Translate Each Ray Condition into an Angle
This short read prepares one exact NSEP pattern: critical-angle constraints in a right prism. Identify the physical condition before calculating.
Critical-Angle Constraints in a Right Prism is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Start with the physical model
Read the configuration once, state the conserved quantity or governing law, and mark any changing geometry, sign convention or limiting condition.
Build the relation
Applying Snell's law to the first arrangement, the emergent ray grazes AC, so the internal incidence there equals the critical angle C. For the second arrangement the incidence at AB must exceed C for total internal reflection.
This corresponds to option B.
Check before selecting
Check units, sign and one limiting case. A valid result must still fit the original geometry and stated constraint.
OlympIQ exam lens
- ✓Name the governing law before using a formula.
- ✓Keep the stated geometry and direction information explicit.
- ✓Use one unit or limiting-case check.
A grazing emergent ray gives equality at the critical angle, whereas total internal reflection requires a strict inequality.
Ready to try the pattern?
100% coverage across the linked question.
Practise the linked question