Oc-4 Michelson Interferometer
AIM
To demonstrate how the Michelson Interferometer works and associated applications.
APPARATUS
- Thor Labs Michelson Interferometer Kit
- Video Camera
DIAGRAM
DESCRIPTION
The Michelson Interferometer is a common configuration used in optical interferometry, using the principle of superposition. It was invented by Albert Michelson in the late 19th century. Refer to the above diagram. A laser beam is split into two perpendicular beams by the use of a beam splitter. The first beam goes straight through the beam splitter and is directed towards an adjustable mirror. The second beam is reflected at 90° towards a fixed mirror. The first beam is reflected 180° by the adjustable mirror towards the beam splitter, it then reflected 90° by the beam splitter towards the screen. The second beam is reflected 180° from fixed mirror back towards the beam splitter, it then goes through the beam splitter towards the screen. When the two beams arrive at the screen, they will either constructively or deconstructively interfere depending on if they are in phase or out of phase. Newton’s Ring Interference pattern can be observed on the screen.
ΔS=S1-S2 is the path length difference between the two mirrors.
The maxima in brightness of the fringes are given by nλ while the minima is given by (n+1/2)λ.
The Michelson Interferometer can used to measure the wavelength of light, determining the refractive index of a material, thickness of a material, etc.
The Michelson Interferometer was famously used by Michelson-Morley in the late 19th Century, to disprove the aether wind theory that stated the speed of light could vary when it was travelling perpendicular to each other.
Recently Michelson Interferometer is used in the detection of gravity waves in the LIGO observatories.