Adjustment and use of the Michelson Interferometer School of Electronics & Applied Physics, Hefei University of Technology

 the experiment of “the ether drift", demarcation of meter ruler, inference of spectral line’s fine structure  Observation of many optical interference (non- localization interference, localization interference; the interference of equal thickness,the interference of equal inclination and so on)  Measurement of micro-length finely  Measurement of refractive index of gas and liquid Synopsis Michelson’s Interferometer Michelson （ ）

Experimental Goals  To grasp adjustment and application methods of the Michelson’s Interferometer  To learn the principle and structure of the Michelson’s Interferometer  To observe the interference of equal inclination  To measure the wavelength of sodium light and difference between the sodium double wavelengths

Teaching Frame  Experiment Principle  Equipment Operation  Data Process Key

Experiment Principle  1. the basic light road half penetration and half reflection film compensation Plate h i n S 1 2 h The Michelson Interferometer light road figure Interference of equal thick thin-film

Experimental principle the interference of equal inclination the interference of equal thickness S n h Localization in infinity The localization near upper surface k i k i

2.the interference of equal inclination The light path difference : ( To air thin film ： n=1 ) Bright stripe Dark stripe ( K=0,1,2…) Experiment Principle The stripes of interference of equal inclination : （1）（1） （ 2 ） Interference stripes density is related to the film thickness h h is overlapped with (a) When h is bigger, the stripe is closer ;h is smaller, the stripe is sparser (b) When h increases, the stripe expands; when h reduces, the stripe shrinks.

 Measurement of wavelength with interference of equal inclination  Measurement of wavelength difference between the sodium double wavelength with the interference of equal inclination Experiment Principle Regarding to central level of stripes (i=0) : Visibility is zero (1) bright dark (2) Visibility is zero again To subtract (1) from (2) and educe experiment formula: bright dark h reducing Δλ= = 0.6nm 2 h =kλ h =kλ/2 h ˊ =(k+1)λ/2

Equipment Operation Two questions must be understood before adjusting the equipment: 1.The condition to obtain the interference of equal inclination: two surfaces of thin film are parallel ( //, namely ⊥ ) 2. In experiment, we observe the stripe diversification of equal inclination by changing film thickness h. ( Including stripe shrinking or expanding, the density and visibility changing, and so on) h The position is adjusted by big knob to remove M2 fleetly and small knob to remove M2 slightly Big knob Small knob Vertical screw mirror M1 mirror M2 Compensation flake Glass flake to separate light Ground-glass Sodium lamp Horizontal screw

 Aim is to adjust a group of concentric cirque stripes in the central field of vision which are clear and stable and have proper density.  Operation Process: 1. To adjust circle center ( To adjust three screws behind mirror M1 and horizontal and vertical screws ) 2. To make the stripe clear and make its density to be proper (To adjust big knob to remove M2. ) 3.To make the stripe stable (To adjust horizontal and vertical screws ) Skill : Before experiment, M2 is adjusted to be about 31mm. It makes the distance from M2 to plate to be approximately equal to the distance from M1 to plate. Equipment Operation big knob Small knob Vertical screw Horizontal screw Plate for dispersion of light Compensation plate mirror M1 Ground-glass Sodium lamp mirror M2

Equipment Operation i N( 条 ) h(mm) Measurement of the sodium light wavelength : Attention:The small knob has to be rotated toward a direction in measurement all the time. If rotating direction was changed, error of vacant journey should appear. Record: There are five significant digits after the decimal point Such as : mm Main ruler Reading window of big knob Small knob Estimate Main ruler Big knob Small knob To use method of gradual difference ：

Equipment Operation Measurement of the wavelength difference of sodium double thread : i h ˊ (mm) Δλ= = 0.6nm Small knob Big knob

Date processing  Demand: The final result is :  Mainly two knowledge spots to be used : 1. method of gradual difference 2. transmission formula of the extent of uncertainty

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