Conceptual Questions Chap. 23

1. Conceptual Questions Chap. 23 A virtual image can be photographed as any object can. Light rays diverge from the position of a virtual image just as they do from an actual object. • Can a virtual image be photographed? Why or why not? • Why does a clear stream always appear to be shallower than it actually is? • Lenses used in eyeglasses, whether converging or diverging, are always designed such that the middle of the lens curves away from the eye. Why? • A common mirage is formed when the air gets gradually cooler as the height above the ground increases. What might happen if the air grows gradually warmer as the height is increased? Light rays from an object at the bottom of the stream are refracted away from the normal to the air–water interface. The resulting refracted rays appear to originate from a point that is closer to the surface than the object that emits them really is. The design is chosen so your eyelashes will not brush against the glass as you blink. Also, when you direct your gaze near the outer circumference of the lens you receive a ray that has passed through the glass with more nearly parallel surfaces of entry and exit. Then the lens minimally distorts the direction to the object you are looking at. An effect similar to a mirage is produced, except the “mirage” is seen hovering in the air. “Ghost” lighthouses in the sky have been seen over bodies of water by this effect.