gen-briefly-explain-the-critical-angle-and-one-common-misconcept-01be

Briefly explain the critical angle and one common misconception about it.

## Critical Angle The **critical angle** is the angle of incidence (measured from the normal) at which light traveling from a denser medium to a less dense medium refracts at exactly 90° along the boundary. At angles greater than the critical angle, total internal reflection occurs instead of refraction. It's calculated using: sin(θc) = n₂/n₁ (where n₁ > n₂) ## Common Misconception **Misconception**: Many people think the critical angle can occur when light travels from any medium to any other medium. **Reality**: The critical angle *only exists* when light travels from a **higher** refractive index medium to a **lower** refractive index medium (e.g., glass to air, water to air). When light goes the opposite direction (air to glass), it simply refracts toward the normal and cannot experience total internal reflection, so there is no critical angle in that situation.