ELI5 + "University project"

Really?

Anyhow, the keywords you need are Refraction https://en.wikipedia.org/wiki/Refraction for why light bends when it enters glass or water etc.,

and Dispersion https://brilliant.org/wiki/dispersion-and-scattering-of-light/

Dispersion is the phenomenon that refractive index isn't actually a constant for a material, but is slightly dependent on the wavelength of the light. This is why prisms split up white light into a "rainbow" spectrum, and why lenses suffer chromatic aberration (unwanted different focus for different colours/and coloured edges on things).