refraction, critical angle and total internal reflection

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

n_{1}sin theta_{i} = n_{2}sin theta_{r}

Usually material 1 is air, and so n_{1} = 1.  This simplifies Snell’s law to

sin theta_{i} = n sin theta_{r}

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

total internal reflection from mr mackenzie on Vimeo.

The critical angle theta_{c} and refractive index n are related by

Here are some applications of total internal reflection here.  You can test your knowledge of refraction with this interactive simulation.

I have attached a pdf with some notes and questions on refraction, total internal reflection and critical angle.