Using the Michelson Interferometer
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Transcript of Using the Michelson Interferometer
Purpose
( 1 ) Learn to use Michelson Interferometer
( 2 ) Study the fringe patterns resulting from a point source, and make a precise measurement of the wavelength of the He-Ne laser
Experiment Principle
dM1'
M1
Mirror
M2
Mirror
S
G1
Beam splitter
G2
CompensatingplateObservation screen
Pointolite Non-localized Interference
SG= S'G 2 2 2S'M =M S'
2R2L2R22d)(LΔL
2d
L
d
S
S'
G
E PR
M 1
M 2
M 1'
S 1'
S 2'
2dcos =k k=0,1,2,
cos2/2 22 dRLLdL
L>>d, ignore , then2 2d /L
The condition of bright fringe is
d
d
L
measuring laser wavelength
When k、 are invariable, with the decrease of d, decreases . Then radius of ring fringe of the same k order decreases, as appears that interference circles contract entad. Similarly with the increase of d, interference circles expand forth. If the fringes in the circle center contract entad or expand forth N times, the variation of optical path difference is 2△d=N, then we have
Nd/2
2dcos =k k=0,1,2, d
Data Reading
Graduated scale Reading data window Fine adjustment drum wheel
xx . xx xxx Graduated scale Reading data window Fine adjustment drum wheel
36.71503mm
Experimental Procedure 1 . Let laser irradiate directly in the middle
of beam splitter, and adjust adjustment screws to make the two biggest and brightest faculae on the observation screen coincide with each other completely.
2. Put the convex lens on the bracket and let the light irradiate on the beam splitter uniformly. Then adjust tension spring screws to move the circle center of the rings to the center of the observation screen.
3 . Rotate the fine adjustment drum wheel in the same direction for some cycles until fringes on the observation screen contract entad or expand forth. Then record the position of M1, which is designated as d0
4. Continue to rotate the fine adjustment drum wheel in the same direction. When contracting entad or expanding forth every 50 fringes, record the position of M1. Ten records should be got.
NoticeNever touch any optical surfaceNever touch any optical surface
Before measuring data, null-space must Before measuring data, null-space must be eliminated. be eliminated.
When measuring, rotate the fine When measuring, rotate the fine adjustment drum wheel only in the same adjustment drum wheel only in the same direction, never rotate reversely. direction, never rotate reversely.