Principle

Along with the Fresnel double mirror experiment, this experiment
with a Fresnel biprism is another one of historical significance
which was performed in the 18th and 19th centuries to demonstrate
the wave theory of light.
The surface of the Fresnel biprism strucked by the light
emitted from a light aperture encompass an angle of almost
180°. If a diverging beam of light strikes the edge of the
biprism, two diverging coherent light beams are created which
appear to emerge from two virtual slits and interfere on the far
side of the biprism. The students should first make themselves
familiar with the general setup of the Fresnel experiment and
describe the interference patterns.

In the second experiment, the wavelength of red light is to be
determined. The students can use the other colour filters (e.g. in
groupwork), to ascertain the wavelength 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

How can refraction bring about interference of light?


Direct a narrow beam of light onto the blunt edge of a
Fresnel biprism and observe what happens.


Measure the distance between the virtual light sources and,
using this and the interference pattern, determine the wavelength
of red light.