Sight is all about light.
Light behaves in very consistent ways.
When light passes through a lens and when we know a little math and science we can predict exactly what will happen.
Light In Materials
The Angle Of Incident & The Normal
It is all about how rays strike a surface and what material that surface is.
Where Does “n” the Index of Refraction Come From?
The material a lens is made from has an index of refraction. The abbreviation for an index is n.