Lesson 3 Mirrors, Lenses, and the Eye: Why are some surfaces mirrors?
We learned that when a smooth surface reflects light rays traveling in the same direction at the same angle this is called regular reflection. When a surface is not smooth the reflected light rays travel in many different directions this is called diffuse reflection.
Types of Mirrors – We learned that any reflecting surface is a mirror. The shape of a mirror’s surface affects how the image appears in that mirror. A plane mirror is a flat reflecting surface. The image is right-side up and reversed left to right. A concave mirror has a reflecting surface that curves inward. Parallel light rays reflect through one focal point. If an object is closer than one focal length from a concave mirror, the image of that object will be right-side up. If the object is more than one focal length from a concave mirror, the image will be upside down. A convex mirror has a reflecting surface that curves outward. Images in this kind of mirror are always right-side up and smaller than the original object.
Types of Lenses – We learned that a transparent object with at least one curved side that causes light to change direction is called a lens. A convex lens curves outward on one side. Like a concave lens, a convex lens has a focal point and a focal length. When an object is less than one focal length from a convex lens the image appears larger and right-side up. A concave lens is curved inward on one side. The image formed by a concave lens appears to be upright, smaller, and closer to the lens than the original object.