Short Answer
n₁ sinθ₁ = n₂ sinθ₂ is the best answer.
Wave and optics questions test how frequency, wavelength, phase, interference, and geometry fit together. Start with the physical picture before choosing the equation.
Snell's law: n₁ sinθ₁ = n₂ sinθ₂ — relating angles and refractive indices at an interface.
Why This Answer Is Correct
This is a Medium-level question in Waves & Optics. The prompt is really testing whether you can connect the concept to its defining physical relationship instead of picking a nearby-but-wrong term.
If a waves question feels messy, sketch the geometry or phase relationship first, then return to the algebra.
Choices At A Glance
- A. n₁ sinθ₁ = n₂ sinθ₂
- B. n₁ cosθ₁ = n₂ cosθ₂
- C. n₁θ₁ = n₂θ₂
- D. sinθ₁/sinθ₂ = n₁
When similar options appear on an exam, eliminate the ones that break the core law, use the wrong units, or confuse a definition with a consequence.
Topic Snapshot
Topic: Waves & Optics
Difficulty: Medium
Best next move: Re-state the governing law in your own words, then solve one more example from the same topic before moving on.