Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can describe the three things that can happen to light at a boundary: reflection, transmission and absorption. (Guide: “Light at a boundary”)
- I can state when a reflected ray has a 180° phase change and when it has none, and explain that refraction never changes the phase. (Guide: “Phase changes on reflection”; Practice Q1)
- I can explain why thin-film colours only appear when the thickness is comparable to the wavelength of light. (Guide: “Light at a boundary” and FAQ)
- I can explain that the amount of interference depends on thickness, wavelength, phase changes and viewing angle. (Guide: “Two reflected rays”)
Calculation and skills
- I can draw a labelled diagram of the two reflected rays from a film and mark the phase change at each surface. (Guide: Figure 1; Practice Q6a)
- I can find the wavelength of light inside a film using λ_film = λ/n. (Guide: “The wavelength inside the film”; Practice Q2)
- I can find which visible wavelengths a film reflects strongly or weakly at normal incidence. (Guide: Worked example 1; Practice Q5)
- I can calculate the minimum thickness of a quarter-wave antireflection coating. (Guide: Worked example 2; Practice Q3)
- I can use two measured reflection minima to find the thickness of a film. (Practice Q7)
Reasoning
- I can explain the black region and the colour bands of a soap film using thickness and phase changes. (Guide: “Soap bubbles and oil films”, Worked example 3; Practice Q4)
- I can justify why a coating’s index must lie between the indices of air and the lens. (Guide: Worked example 2c; Practice Q6)
- I can predict which way a reflection minimum moves when a film gets thinner. (Practice Q7d)
- I can explain where the energy goes when reflected light cancels. (Guide: “Antireflection coatings” and FAQ)
All ticked? Move on to Topic 15.1: Quantum Theory and Wave-Particle Duality, or return to the course roadmap.