Diffraction at a system of circular apertures of equal size

Principle

The students should recognize that, just as in diffraction from a slit grating (a system of equidistant slits of equal width), diffraction occurs from a system of equidistant, circular apertures of equal diameter.

All the circular apertures produce the same diffraction pattern because they all have (approximately) the same diameter. The superposition of all these diffraction patterns creates the concentric circies observed in the experiment, the diameter of which is dependent on the wavelength of the light employed - providing that all other aspects of the set-up remain unchanged -, and these circles reflect the arrangement of the holes in the diaphragm.

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

1. Direct a narrow beam of Iight of circular cross-section onto a diaphragm perforated by identical holes of small diameter.
2. Investigate the interference patterns created when, firstly, these holes are arrayed at regular intervals, and secondly, when they are arrayed at random.
3. With the aid of the diffraction patterns calculate the diameter of the holes.