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Deviation of an electromagnetic wave from the path that is predicted by geometric optics because of the wave's interaction with a physical object that stands in its path is known as diffraction. Light bending around non-transparent physical bodies and the penetration of light into the area of the geometric shadow is an example of light diffraction.

The phenomenon of diffraction imposes certain limitations on the quality of telescopic resolution. A complex picture is formed because of diffraction in the telescope's focal plane. An image of a star is not a point but, rather, a bright circle that is surrounded by black and white rings. Such a circle is a direct outcome of diffraction. This phenomenon is mainly manifested when one observes bright stars under high magnification. The light rings of weaker stars are virtually invisible, only the central maximum can be seen. The angular radius of the star disk diffraction is

δ = λ/D.

This model illustrates a particular type of diffraction known as the Fraunhofer diffraction. A beam of light falls on an obstacle. According to Huygens' principle, any point of the wave front becomes a source of secondary radiation. In accordance with this principle, light bends around obstacles of sizes comparable to its wavelength. Once the light beam passes the obstacle and reaches the screen, a pattern of rings or lines comes into view.

Specify the type of obstacle you would like to observe by selecting an appropriate switch. Use the model's upper window to set obstacle sizes. The wavelength may be selected by using a special control element. Diffraction procedure is m, and L is the distance between the object and the screen.

© OpenTeach Software, 2007