The refractive index of a transparent material can be measured using a 20° prism
of the material.
A ray of light is incident perpendicularly to one face and passes straight into the
prism. The angle of refraction r, as it leaves the prism, can be measured and the
refractive index of the material calculated.
By making suitable calculations suggest whether it is possible to distinguish
between diamond and zircon using a protractor to measure the angles