Light - Reflection and Refraction Cheat Sheet

Key Definitions

• Reflection: Bouncing back of light when it strikes 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

Reflection

• Law of Reflection: i = r

• Types:

• Specular (smooth surfaces)

• Diffuse (rough surfaces)

Refraction

• Snell's Law: n1 sin(i) = n2 sin(R)

• Critical Angle: Angle of incidence that results in an angle of refraction of 90°.

• Total Internal Reflection: Occurs when light attempts to move from a denser to a rarer medium beyond the critical angle.

Key Formulas

• Snell's Law:

 
  n1  sin(i) = n2  sin(R) 
  

• Refractive Index (n):

  n = c / v
  

• c: Speed of light in vacuum

• v: Speed of light in medium

Common Mistakes to Avoid

Common Mistake: Confusing angle of incidence with angle of reflection.

Memory Tricks

Tip: "RIR" — Reflection = Incidence = Reflection (i = r)

Key Diagrams

        Incident Ray
          \
           \
            \
             | i
             |
             |  Normal
             |
             | r
             /
            /
           /
          Reflected Ray

        Medium 1       Medium 2
          |              |
          |              |
          |              |
          |              |
          |              |
          \              /
           \            /
            \          /
             \        /
              \      /
               \    /
                \  /
                i

Tip: Practice drawing diagrams to visualize concepts better.