Chapter 13: Section 3

Learning Targets Describe the difference between a real and a virtual image Draw ray diagrams for objects located at various distances from concave mirrors Draw ray diagrams for objects located at various distances from convex mirrors

Curved vs. Flat Mirrors Images formed by curved mirrors differ from those formed by flat mirrors Depending on the object location, the image could be enlarged or reduced in size The image could also be inverted or upright

Concave Spherical Mirrors A spherical mirror with light reflecting from its silvered, concave surface, is called a concave mirror Concave mirrors are capable of forming both real and virtual images

What is a Real Image??? A reflected image that appears to lie in front of the reflecting surface is called a real image This is in contrast to a virtual image which appears behind the mirror. When a real image is produced, that image can be obtained on a screen placed in front of the mirror

Ray Diagrams for Concave Mirrors There are two rules of reflection for concave mirrors. Any incident ray traveling parallel to the principal axis will pass through the focal point upon reflection. Any incident ray passing through the focal point will travel parallel to the principal axis upon reflection

Real or Virtual? Real images are formed when: Objects are located behind the center of curvature Objects are located at the center of curvature Objects are between the center of curvature and the focal point

Virtual images are formed when: Objects are located in front of the focal point

If an object is located at the focal point, the reflected rays never cross. Therefore no image is formed

Concave Mirror Practice

Convex Spherical Mirrors The passenger’s side mirrors on a car bulge outward at the center Images in this mirror are distorted near the mirror’s edges, and the image is smaller than the object This type of mirror is called a convex spherical mirror

Convex mirrors are also called diverging mirrors because incoming light rays diverge after reflection The resulting image is always virtual

Negative Focal Length For a convex mirror, the center of curvature and the focal point are located behind the mirror. Since the focal point is located behind the convex mirror, such a mirror is said to have a negative focal length value

Convex spherical mirrors take the objects in a large field of view and produce a small image This makes them well suited for providing a complete view of a large area They are often placed in stores or busy hallways

Ray Diagrams for Convex Mirrors Any incident ray traveling parallel to the principal axis will reflect from the mirror and its extension will pass through the focal point This extension is represented by a dashed line Any incident ray traveling towards a convex mirror such that its extension passes through the focal point will reflect and travel parallel to the principal axis

Image for Convex Mirrors Located behind the convex mirror A virtual image Always upright Reduced in size (i.e., smaller than the object )

The diagram below illustrates that as the object distance is decreased: the image distance is decreased the image size is increased So as an object approaches the mirror, its virtual image approaches the mirror and becomes larger.

Convex Mirror Practice