Adjustment and use of the Michelson Interferometer

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Adjustment and use of the Michelson
Interferometer

• School of Electronics Applied Physics,
• Hefei University of Technology

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Synopsis
Michelson( 1852 -1931)
Michelsons Interferometer

• the experiment of the ether drift", demarcation
  of meter ruler, inference of spectral lines
  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
  

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Experimental Goals

• To grasp adjustment and application methods of
  the Michelsons Interferometer
• To learn the principle and structure of the
  Michelsons Interferometer
• To observe the interference of equal inclination
• To measure the wavelength of sodium light and
  difference between the sodium double wavelengths

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Teaching Frame

• Experiment Principle
• Equipment Operation
• Data Process

Key
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Experiment Principle

• 1. the basic light road

h
S
1
i
n
h
2
Interference of equal thick thin-film
The Michelson Interferometer light road figure
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Experimental principle
the interference of equal inclination
the interference of equal thickness
The localization near upper surface
Localization in infinity
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Experiment Principle

• 2.the interference of equal inclination
• The light
• path difference

The stripes of interference of equal
inclination
Bright stripe
( K0,1,2)
(1)
Dark stripe
( K0,1,2)
(To air thin film n1)
(a) When h is bigger, the stripe is closer h is
smaller, the stripe is sparser
(2) Interference stripes density is related to
the film thickness h
(b) When h increases, the stripe expands when h
reduces, the stripe shrinks.
is overlapped with
h
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Experiment Principle

• Measurement of wavelength with interference
• of equal inclination
• Measurement of wavelength difference between the
• sodium double wavelength with the interference of
  equal inclination

Regarding to central level of stripes (i0)
2h k? h k?/2 h (k1)?/2
h reducing
Visibility is zero
(1)
bright
dark
(2)
Visibility is zero again
bright
dark
To subtract (1) from (2) and educe experiment
formula
?? 589.6 - 589.0 0.6nm
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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)

Glass flake to separate light
mirror M2
Compensation flake
Sodium lamp
mirror M1
Ground-glass
Horizontal screw
h
Big knob
Vertical screw
Small knob
The position is adjusted by big knob to
remove M2 fleetly and small knob to remove M2
slightly
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Equipment Operation

• 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
• 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

Plate for dispersion of light
Compensation plate
mirror M2
mirror M1
Sodium lamp
Ground-glass
Horizontal screw
big knob
Small knob
Vertical screw
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Equipment Operation
Measurement of the sodium light wavelength
i 0 1 2 3 4 5
N(?) 0 50 100 150 200 250
h(mm)
Main ruler
AttentionThe 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.
Reading window of big knob
To use method of gradual difference
Record There are five significant digits after
the decimal point Such as 31.45 67 8mm
Small knob
Main ruler
Estimate
Big knob
Small knob
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Equipment Operation
Measurement of the wavelength difference of
sodium double thread
i 1 2 3 4 5 6
h(mm)
Big knob
Small knob
?? 589.6 - 589.0 0.6nm
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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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Thank you!