Diffraction at a crossed grating

Principle

A crossed grating consists of two systems of diffraction slits positioned at right angles to each other. This can best be accomplished by crossing two line gratings. When light is diffracted from a crossed grating, it produces interference patterns with a reticular structure. If the crossed gratings have the same grating constant, the mesh shape will be square, and if not it will be rectangular. In the experiment the two gratings employed have grating constants in the ratio of 1 : 2; hence diffraction patterns with rectangular mesh holes are produced, the sides of which are in the ration of 2 : 1.
Working first with white and then with red light, the students should in the course of the experiment become acquainted with this kind of meshed diffraction pattern.

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

Direct a parallel, narrow beam of Iight onto two line gratings positioned crosswise to each other, and investigate the ensuing interference patterns.