Experiment No. 2: Michelson's interferometer

Introduction


Interferometers are the devices, by which very fine optical path changes of one of the interfering rays can be measured. We are able to find out imperfections of polished surfaces, different defects of transparent materials, or simply measure a refraction index of some medium using an interferometer.
Michelson's interferometer consists of one semitransparent mirror and two mirrors. Semitransparent mirror SM splits the beam into two ones perpendicular to each other, propagating in the two arms of the interferometer. These beams are reflected by the mirrors M1 and M2. Then they go back through the arms and after transmission of the semitransparent mirror they join again. The beams are carrying an information about the length of the arms. The position of the interference fringes depends on the difference of the mirrors distances from the semitransparent mirror SM.
Objective


To observe an interference pattern using Michelson's interferometer.
Equipment

Laser (635 nm), ground screen, 2 mirrors, 1 semi-transparent mirror, lens.