1. The focal length of a simple lens is different for different colors of light. Why?

2. A bird above the water is viewed by a scuba diver submerged beneath the water's surface directly below the bird. Does the bird appear to the diver to be closer to or farther from the surface than it actually is?

3. Convex mirrors are often used for rear-view mirrors on cars and trucks to give a wide-angle view. Below the mirror is written, “Warning, objects are closer than they appear.” Yet according to a ray diagram such as Figure, the image distance for distant objects is much smaller than the object distance. Why then do they appear more distant?