Let's tackle subtraction first. Subtraction in hexadecimal works similar to subtraction in decimal. Let's do a pair of decimal problems and see if we can parallel the solution method in hex. Suppose we want to subtract 1586 - 243 (in decimal).
Refraction of Light Rays. the bending or deflection of light rays as they pass through the various media of the eye that include the conjuctiva, cornea, aqueous humor, lens, and vitreous body.
The Prism. The prism in eyeglasses bends light. It is placed in the glasses so that as the eyes look through them, the objects are pulled into focus. It is similar to a triangle or cone. The focus occurs because the bottom of the prism is on the outside of the glasses.