Reflection of Light

Reflection of light (and other forms of electromagnetic radiation) occurs when the waves encounter a surface or other boundary that does not absorb the energy of the radiation and bounces the waves away from the surface. This tutorial explores the incident and reflected angles of a single light wave impacting on a smooth surface.

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The tutorial initializes with a red sinusoidal wave incident on a smooth, mirrored surface at an angle of 40 degrees. The incident light is reflected from the surface according to the Law of Refraction and leaves with the same angle at which it arrives. The Wavelength and Incident Angle sliders can be utilized to adjust these parameters of the wave, which will be immediately executed in the tutorial. Beneath the sliders, the mathematics involved in calculating the angle of the reflected wave is reviewed for each incident and reflected angle as the Incident Angle slider is adjusted.

When light reflects from a smooth surface, the incoming light wave is referred to as an incident wave, and the wave that is bounced away from the surface is termed the reflected wave. Visible white light that is directed onto the surface of a mirror at an angle (incident) is reflected back into space by the mirror surface at another angle (reflected) that is equal to the incident angle, as presented in the tutorial for the action of a sinusoidal light wave on a smooth, flat mirror. Thus, the angle of incidence is equal to the angle of reflection for visible light as well as for all other wavelengths of the electromagnetic radiation spectrum. This concept is often termed the Law of Reflection. It is important to note that the light is not separated into its component colors because it is not being "bent" or refracted, and all wavelengths are being reflected at equal angles. The best surfaces for reflecting light are very smooth, such as a glass mirror or polished metal, although almost all surfaces will reflect light to some degree.

Contributing Authors

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