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 Physics Classroom says: This bending of the path of light is known as refraction. It happens at the boundary or interface between two distinctly different materials. It occurs because light changes speed as it passes into a new material. This change in speed is accompanied by a change in direction.