Mirages are caused by changes in the atmosphere just above the ground. Light rays traveling through hot air are bent as they hit cooler air. "Fata Morgana" - Found in the straits of Messina near Italy. Ships and whole cities appear in the sky inverted or right side up.
Found in the Harz mountains of Germany. Huge shadows with rings of light are cast upon fog banks when the sun is low in the sky.
"Pepper's Ghost" - Was a stage technique of the early 1900's. A clear sheet of glass was set up between the stage and the audience. The reflection of the actor positioned beneath the stage was seen on the stage as a "ghost". The other actors on stage could walk through the ghost.
Depth Illusions - They occur when light rays bend as they travel from water to air. The observer's eyes follow the rays back in a straight, not bent, line. A virtual image of an object is formed above the actual object in the water.