A prism is a cut piece of clear glass or plastic in the form of a triangular prism that separates white light into a spectrum through ?

Refraction

Explanation:

The speed of light depends on the medium in which it travels. For example, light travels slower in water than in air because water is denser.

This is related to prisms because light, when entering a prism will travel slower, so it will change direction, this is known as refraction and is the reason why prisms produce rainbows (spectrum).

White light is made up of different wavelengths, as each of these wavelengths passes through the prism it separates the light because each one will travel at a different speed and this difference in speed causes each wavelength to be refracted in a slightly different direction, causing white light to break down into the colors of the visible spectrum.

a.   mass number from atomic number