Table Of Contents: Reflection and Mirrors
1. Plane Mirrors
A plane mirror is typically formed from a smooth glass surface with a silver painted back. A regular reflection is formed when light reflects off a plane mirror. When you look in a plane mirror, the image you see is a virtual image. Virtual images don’t exist unless someone is there to see it. In the plane mirror, your image appears to be behind the mirror but is not actually there. The virtual image formed by a plane mirror is upright, the same size as the object, but reversed left to right.
2. Curved Mirrors
Curved mirrors have an optical axis. The optical axis is an imaginary line that divides the mirror in half. The point on the optical axis where distant light rays meet when reflected, is called the focal point. The distance from the focal point to the mirror is called the focal length, f. The distance from the object to the mirror is the object distance. The distance from the image to the mirror is the image distance.
3. Ray Diagram of a Mirror
A ray diagram is used to locate an image. Where is the image of the hammer? A line is drawn from the top of the hammer to the mirror, parallel to the optical axis. The reflected ray is drawn from the mirror through the focal point. Another ray is drawn from the top of the hammer, through the focal point, to the mirror. The reflected ray is drawn from the mirror and is parallel to the optical axis. The lines will meet at a point showing the location of the image.
4. Concave Mirrors
A concave mirror has a surface that curves inward. Two kinds of images can be formed when light reflects off a concave mirror. If the object is farther away than the focal point, a real image is produced. A real image can be projected on a screen. The image produced is upside down and can be smaller or larger than the object. When the object is at the focal point, no image is seen. A virtual image is formed when the object is between the focal point and the mirror. The rays of light never actually meet, but appear to meet behind the mirror. The virtual image is upright and larger than the object.
5. Convex Mirrors
A convex mirror has a surface that curves outward. The rays reflected from a convex mirror will never meet. The reflected rays appear to meet behind the mirror, producing a virtual image. The image is upright and smaller than the object. Convex mirrors are useful because they allow you to see a larger field of view.