A Michelson interferometer can be used for a variety of applications including wavelength measurement, flow visualisation and, as recently seen, in the detection of gravitation waves. In this simulation you can investigate the operation of a Michelson interferometer including its application to measuring the refractive index of a test gas inserted in one arm of the interferometer. Note that the simulation is best viewed using a web browser on a computer. However, the simulation may also be viewed using any internet-enabled mobile device.
In a Michelson Interferometer, light from a source of wavelength, λ, is divided into two paths by a beamsplitter. After reflection from back mirrors, the two beams are recombined and interfere, the pattern of which is determined by the length of the path taken by each beam. Familiarise yourself with the interferometer simulation and ensure that you understand the effect of varying the mirror separation, d, (the difference between the length of the two arms of the interferometer), and the tilt of one end mirror described by the angle, α.
Consider a configuration for a Michelson Interferometer in which a test cell is mounted in one arm of the interferometer. A change in pressure in the cell changes the density of the gas which, in turn, changes the refractivity of the gas (n-1 where n is the refractive index). This changes the effective length of the arm of the interferometer.
The simulation can be used to explore how the fringe pattern varies with pressure in the cell, and to directly measure the refractivity of the gas in the cell (the cell length is 1.0cm). This can be tested on a known gas (the refractivity of air is 2.92x10-4) or an unknown gas (selected randomly by typing any number into the "Code" box).