### Overview

Prisms are optical elements made of an optically active medium which serve to bend and/or reflect light. Some prisms are also notable for their ability to disperse light into component colors. In shape, these elements generally resemble geometric prisms although not all optical prisms are geometric prisms, and vice-versa.

### Tutorial

The K-Optics starter’s kit comes equipped with a 5 piece prism set. These prisms are used in the __Ray Optics Experiment__, with varying purposes. The rectangular and triangular prisms are used to exhibit the law of specular reflection, while the lens-shaped prisms are used in the lens part of the ray optics experiment. Finally, the semicircular prism is used to exhibit Snell’s law, as well as collimation of rays exiting the __DoE__ in the lens part of the experiment.

### Theoretical Background

A prism's operating principle is the law of refraction, also known as Snell’s law. Snell’s law simply relates the angles of incidence and transmission. This relation assumes knowledge of the incoming ray’s angle of incidence, as well as the refractive indices of the optic media.

Snell’s law can be shown simply by applying Hero’s principle of least distance in homogeneous media on a geometric scheme.

Two parallel rays encounter an interface between media at points A and D, respectively. Denote the time between arrival of the two rays at the interface Δt. In that time ray CD propagates a distance

At the same time, ray BA propagates a different distance in the other medium.

Applying the law of sines to triangles ∆AHD and ΔAGD, we arrive at

By definition,

Such that

All prisms exploit this law to bend light, and a prism’s effect on light can be calculated by repeated applications of this law at every interface between optic media.