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.
Light waves travel out from their source in straight lines called rays. Rays do not curve around corners, so when they hit an opaque object (one that does not allow light to pass through it), they are blocked from reaching the other side of that object. We see a dark shadow in the area from which light is blocked.