We met refraction during the National 5 course. At Higher level, we are interested in the relationship between the angles of incidence (θi) and refraction (θr).
Snell’s law tells us that
Usually material 1 is air, and so . This simplifies Snell’s law to
where n is the absolute refractive index of material 2. Since the refractive index is equal to the ratio of the ray’s speed (v) in materials 1 & 2 and also equal to the ratio of the wave’s wavelength (λ) in materials 1 & 2, we can show that
Read more about Snells’s law here.
total internal reflection
The critical angle and refractive index n are related by