Basic Properties of Mirrors

Section Overview:

Reflection of light is an inherent and important fundamental property of mirrors, and is quantitatively gauged by the ratio between the amount of light reflected from the surface and that incident upon the surface, a term known as reflectivity. Mirrors of different design and construction vary widely in their reflectivity, from nearly 100 percent for highly-polished mirrors coated with metals that reflect visible and infrared wavelengths, to nearly zero for strongly absorbing materials.

The images formed by a mirror are either real or virtual, depending upon the proximity of the object to the mirror, and can be accurately predicted with respect to size and location from calculations based on the geometry of any particular mirror. Real images are formed when the incident and reflected rays intersect in front of the mirror, whereas virtual images occur at points where extensions from incident and reflected rays converge behind the mirror. Planar (flat) mirrors produce virtual images because the focal point, at which extensions from all incident light rays intersect, is positioned behind the reflective surface.

Introduction to Mirrors

Predating even crude lenses, mirrors are perhaps the oldest optical element utilized by man to harness the power of light. Learn about the history, function, and the importance of the mirror in microscopy today. Also, explore the relative similarities and differences to other elements of microscopy such as curved mirrors which are roughly divided into two categories, concave and convex, terms that are also used to describe the geometry of simple thin lenses.

Interactive Tutorials

• Concave Spherical Mirrors

Explore how moving an object farther away from the center of curvature affects the size of the real image formed by the mirror as well as the effects of moving the object closer to the mirror at various points to form a virtual image.

• Convex Spherical Mirrors

The image result of an object reflected by a convex mirror is typically virtual, upright, and smaller. Discover how moving the object farther away from the mirror's surface affects the size of the virtual image formed behind the mirror.

• Concave Spherical Mirrors (3-Dimensional Version)

Explore how moving the object farther away from the center of curvature affects the size of the real image formed by the mirror in this interactive tutorial.

• Convex Spherical Mirrors (3-Dimensional Version)

Examine how moving an object farther away from the mirror's surface affects the size of the virtual image formed behind the mirror with three-dimensional graphics.

Contributing Authors

Kenneth R. Spring - Scientific Consultant, Lusby, Maryland, 20657.

Matthew Parry-Hill, Christopher A. Burdett, Robert T. Sutton, Thomas J. Fellers and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.