Grade 11 physics
Wave Optics I: Huygens' Principle, Reflection, Refraction, Total Internal Reflection
Wavefront construction explains reflection and refraction and predicts when light is totally internally reflected at a boundary.
1. Core ideas and learning goals
- Huygens' principle treats each point of a wavefront as a source of secondary wavelets whose envelope forms the next front.
- The angle of reflection equals the angle of incidence, both measured from the normal.
- Snell law relates angles and refractive indices: n1 sin(theta1) = n2 sin(theta2).
- Total internal reflection is possible only from higher refractive index to lower index above the critical angle.
- Optical fibres guide light mainly by repeated total internal reflection while bends and material absorption cause losses.
2. Physical model
Wavefront construction explains reflection and refraction and predicts when light is totally internally reflected at a boundary.
Wavefront construction explains reflection and refraction and predicts when light is totally internally reflected at a boundary. The model links observable changes with measurable physical quantities and conservation laws.
Before applying a relation, specify the reference frame, system boundary, initial state and approximations. The conclusion is valid only while those conditions are satisfied.