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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 indexofgas and liquid
Synopsis
Michelsons Interferometer Michelson1852 -1931
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Experimental Goals
To grasp adjustment and application methods of
the Michelsons Interferometer
To learn the principle and structure of theMichelsons 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
1M2M
1G
2G
half penetration
and half reflection film compensation Plate
'1
hi
n
S
1
2
'
1
'
2
'
i
h'1
'2
The Michelson Interferometer
light road figure
Interference of equal thick thin-film
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Experimental principlethe interference of equal inclination the interference of equal thickness
S
n
h
Localization in infinityThe localization near upper surface
S
O
1M
1
M
e
ki ki
S
K
1K
A
'22cos2sin2 inhinh
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2.the interference of equal inclinationThe light
path difference:'22
cos2sin2 inhinh
(To air thin filmn=1)
2)12(cos2 '
K
K
ih
Bright stripeDark stripe
(K=0,1,2)
(K=0,1,2
)
Experiment Principle
The stripes of interference of equal inclination :
1
2Interference stripes density isrelatedto the film thickness h
'
1M
2M
h'
1M
2M 2M
'
1M'
1M 2Mis 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.
2M
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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):
2
Nh
21111 )2
1( KK Visibilityis zero(1)
bright dark
(2)22122 )
211( KK Visibility is zero again
To subtract (1) from (2) and
educe experiment formula:)3.589(
'2
2
nmh
bright dark
'
1h
'2h
h
reducing
= 589.6 589.0 = 0.6nm
2h=kh=k 2h=(k+1) 2
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Equipment OperationTwo 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)
'
1M2M 2M 1M
'1M
2M
hThe position is adjusted by big knob to remove M2 fleetly
and small knob to remove M2 slightly2M
Big knobSmall knob Vertical screw
mirror M1
mirror M2Compensation flake
Glass flake to separate light
Ground-glass
Sodium lamp
Horizontal screw
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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)
Ski l l : Before exper iment, M2 is adjusted to be about 31mm. I t makes the
distance from M2 to plate to be approximately equal to the distance fr om M1 to plate.
Equipment Operation
big knobSmall knob Vertical screw
Horizontal screw
Plate for dispersion of light
Compensation plate
mirrorM1
Ground-glass
Sodium lamp
mirror M2
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Equipment Operation
i 0 1 2 3 4 5
N() 0 50 100 150 200 250
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.
)50(/2 NNh
)]()()[(
3
1
3
1251403 hhhhhhh
Record:There are five significant digitsafter the decimalpoint
Such as: 31.45 67 8mm
Main ruler
Reading window of big knob
Small knob
EstimateMain ruler Big knob Small knob mm20001.0
To use method of
gradual difference
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Equipment OperationMeasurement of the wavelength difference of sodium double thread:
i 1 2 3 4 5 6
h(mm)
)3.589('2
2
nmh
= 589.6 589.0 = 0.6nm)]()()[(
3
1
3
1362514
'hhhhhhh
'
1h
'
2h
'
3
h
Small knobBig knob
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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)]()()[(
3
1
3
1
362514
'hhhhhhh
)]()()[(3
1
3
1251403 hhhhhhh
%100
/
E
nmmm
{
hh
Nh
22
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Thank you