gen-define-total-internal-reflection-and-give-one-short-worked-e-0efb

Define total internal reflection and give one short worked example.

# Total Internal Reflection **Definition:** Total internal reflection occurs when light traveling in a denser medium strikes the boundary with a less dense medium at an angle greater than the critical angle, causing all the light to be reflected back into the denser medium (with no refraction occurring). ## Conditions Required: 1. Light must travel from denser to less dense medium (higher to lower refractive index) 2. Angle of incidence must be greater than the critical angle The critical angle θc is given by: **sin θc = n₂/n₁** (where n₁ > n₂) --- ## Worked Example **Problem:** Calculate the critical angle for light traveling from glass (n = 1.5) into air (n = 1.0). **Solution:** Using sin θc = n₂/n₁ sin θc = 1.0/1.5 = 0.667 θc = sin⁻¹(0.667) **θc = 41.8°** **Conclusion:** Any light ray hitting the glass-air boundary at an angle greater than 41.8° (measured from the normal) will be totally internally reflected. This principle is used in optical fibers, binoculars, and periscopes.