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.
These rays do not bend. The light rays that reflect from the stems in the water travel back through the water before they reach the air. Light travels faster through air than it does through water. When these rays move into the air, they change speed and bend. Your eyes have convex lens.