What is Snell’s Law and What Does It Mean?
Snell’s Law is the building block of all optical theory. If you grasp the concept of Snell’s Law, you understand how lenses work. Snell’s law explains how the materials from which we make lenses influences the way light bends at specific angles. Snell’s law describes how a ray of light changes course while traveling from one material of a specific index to another material of a different index. An ophthalmic lens, or eyeglass lens, is being bombarded by thousands of rays of light passing through the air. These rays of light strike the lens, and as the ray passes through the lens, we hope to alter its course. For the optician using Snell’s Law, it is best to consider what happens if the ray of light is traveling from a less dense medium (air) to a more dense medium (like polycarbonate) exiting the lens and entering the eye. When a ray travels from a less dense medium to a denser medium, the ray will bend toward the normal. The normal is an imaginary line perpendicular to the medium surf
