Light — Reflection and Refraction Cheat Sheet

Key Definitions

• Reflection: Bouncing back of light when it hits a surface. ✅

• Refraction: Bending of light as it passes from one medium to another. ✅

• Normal Line: Perpendicular line to the surface at the point of incidence. ✅

• Angle of Incidence (i): Angle between the incident ray and the normal. ✅

• Angle of Reflection (r): Angle between the reflected ray and the normal. ✅

• Angle of Refraction (R): Angle between the refracted ray and the normal. ✅

Important Concepts

Laws of Reflection

• Law 1: Angle of incidence is equal to the angle of reflection. ✅

• Law 2: Incident ray, reflected ray, and normal lie in the same plane. ✅

Laws of Refraction (Snell's Law)

• Snell's Law: n1 sin(i) = n2 sin(R) ✅

• n1: Refractive index of the first medium. ✅

• n2: Refractive index of the second medium. ✅

Total Internal Reflection

• Occurs when light attempts to move from a denser to a rarer medium and the angle of incidence exceeds the critical angle. ✅

Key Formulas

• n: Refractive index. ✅

• c: Speed of light in vacuum. ✅

• v: Speed of light in the medium. ✅

Critical Angle (C) = sin^(-1)(n2/n1) ⚠️

Common Mistakes to Avoid

Common Mistake: Confusing the angle of incidence with the angle of refraction.

Memory Tricks

Tip: "I Really Reflect" — Incident, Reflected, Refracted.

Key Diagrams

        Incident Ray
              \
               \
                \   Normal
                 |\
                 | \
                 |  \
                 |   \
                 |    \
        Reflected Ray  \
                      Refraction