The blind spot in an eye is a point on the retina where light doesn't fall. The illusion of a candle burning under water was created using a prism and the principle of total internal reflection. Microwaves undergo a reflection from a fine wire screen. According to Huygens' principle light waves spreading out from a point source could be regarded as a superposition of tiny secondary wavelets and that every point on any wave front may be regarded on a new point source of waves. Red is bent the most when it travels through a .
Polarized light is depolarized when reflected from a grainy projection screen.
A neon sign will eventually burn-out once all the atoms wear out because of energy losses. The light from a laser is coherent.