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Single-Slit Diffraction

This applet shows the simplest case of diffraction, known as single slit diffraction. You can change the color of the light by dragging or clicking the spectrum selector. You may also change the width of the slit by dragging one of the sides.


Diffraction is a phenomenon which involves the bending of waves around obstacles. It's generally guided by Huygen's Principle, which states: every point on a wave front acts as a source of tiny wavelets that move forward with the same speed as the wave; the wave front at a later instant is the surface that is tangent to the wavelets. If you consider diffraction through a slit, then the properties of the system are dependent on the ratio lambda/ W, where lambda is the wavelength of the light and W is the width of the slit. If you map the intensity pattern along the slit some distance away, one will find that it consists of bright and dark fringes. In the middle a central bright fringe can be found, it is the largest bright fringe. The angle at which the dark fringes occur is given by As you see the intensity pattern is determined only by the ratio lambda/ W. Notice the effect of both the slit width and wavelength by dragging the slit sides and spectrum selector.

� Copyright 1997, Sergey Kiselev and Tanya Yanovsky-Kiselev
Last modified: June 20, 1997