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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

)


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


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

mkes

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