Principle

This double mirror experiment devised by Fresnel in 1816 is one
of a number of experiments of historical significance which were
performed in the 18th and 19th century to demonstrate the wave
theory of light. Using two plane mirrors set at an angle to each
other of almost 1800 ,two virtual light sources are created by
reflection of a diverging beam of light from which two divergent
light beams appear to emerge. These are coherent and can thus
interfere.

The students should first familiarize themselves with the
general set-up of the Fresnel experiment and describe the
interference patterns. The angle of the two mirrors remains
constant which simplifies the set-up.
In the second experiment, the wavelength of red light is to be
determined. You have the Option of using the other colour filters
to ascertain the wavelengths of further colours.


Benefits


Multifunctional light box - All-in-one: Can be used for geometric optics on the table, colour mixing and on an optical bench

Extension with others sets at anytime, no additional light sources needed, recognition value for students



Tasks


Let a narrow beam of light shine onto a Fresnel double mirror
and observe what happens.

Determine the distance from the virtual Iight source and, using
this and the interference pattern, find out the wavelength of red
light.