Sam notices that he can see himself in a spoon. If he's looking at the "bowl" side of the spoon and is 15 cm away and the spoon has a focal point of 10cm, where is his image and what are its characterstics?
The spoon represents a concave mirror, where the curvature is on the inside, where the "bowl" of the spoon is located. If the focal point is 10 centimeters, Sam is more than one focal length away, being at 15 centimeters. The image Sam is seeing will be real (meaning it can be projected onto a screen) and inverted, in the "upside-down" position. Concave mirrors can also produce virtual images, images through which light does not actually travel. Real images are produced by the intersection of light rays outside the focal point. The focal point is the intersection of all light rays traveling parallel to the mirror, then being reflected. The distance between the mirrors surface and the focal point is called the focal length. Concave mirrors are useful in the automotive and flashlight industry in the design of head lamps and flashlights with which to see.