Prism, Refraction, & Reflection

As light moves from one medium to another, it will change speed. This change in speed will change the direction of the passing light ray, and this process is known as refraction. For example, as light travels through air into another medium such as water the speed of the light will move slower. This change in direction and speed is how we are able to create optical lenses. Light will either be reflected off a surface, refracted through a surface, or be absorbed (total internal reflection ie critical angle, which we will talk about later in more depth).

The speed of light in a medium is dependent on the medium itself and the index of that medium. The index of refraction tells us how quickly light will bend through a given material. The higher the index of refraction, the slower light moves through that medium which in turn bends light quicker. The quicker light bends through a material the less of that material is needed to converge light to a focal point. This is why high index lenses (higher indexes of refraction) are thinner than lenses with the same focusing power but lower indexes of refraction.

The index of refraction is notated as “n” in many optical formulas. For example a lens with a power of -6.00 diopters with an index of refraction of 1.67 will be thinner than a -6.00 diopter lens with an index of refraction of 1.49.

Prism

As light enters into a prism it is deviated towards the BASE.

Viewing objects through a prism moves the object towards the APEX.

Dispersion

When white light travels through a prism the colors are broken apart. The colors are broken apart because shorter wavelength colors such as purple slow more than red ones. Here is a quick video on Dispersion.

https://www.khanacademy.org/science/physics/geometric-optics/reflection-refraction/v/dispersion