Refraction & Dispersion

Aim: To investigate refraction, dispersion and total internal reflection using a ray model.

1. Pick materials for the top and bottom media, keeping the top medium as air to start with.
2. Change the incident angle θᵢ and observe the refracted ray. Use Snell's law and the readout values to check that n₁ sin θᵢ = n₂ sin θt for a few angles.
3. Swap the media so light travels from the denser to the less dense medium, then increase θᵢ until you reach the critical angle and total internal reflection occurs.
4. Move the wavelength slider λ and observe how the refractive index n(λ), and therefore the refraction angle θt, changes for a fixed incident angle.
5. Switch to the Waves view and compare the wavelength either side of the boundary with the ray-model picture.
6. Why does the critical angle depend on wavelength? What would you expect to happen to a beam of white light as it approaches the critical angle from inside a denser medium?