MICHLESON
INTERFEROMETER NA LAMP
GROUP -10
SIDHANT
TARUSH
VISHAL
HYPOTHESIS
If we replace sodium lamp with white light we can observe different fringe spacing and
different fringe widths and wavelengths for different colours which comprise white light.
Also only one white spot will be seen in centre and it will be surrounded by rings of
different colours or mixture of colours which comprise white light (i.e VIBGYOR)
VARIABLES
• Independent variable: Angle of the mirrors M1 and M2, Angle of the beam splitter
• Dependent variable: Fringe pattern
CONTROL EXPERIMENT
• Positive control- we use the fine micrometer to change the position of mirror and
observe different fringes of different colours
• Negative control- if the optical path length is not zero interference fringes are not
observered
ERROR ANALYSIS
CALCULATIONS
• The formula for calculating the actual mirror movement is Δd=(ΔNλ)/2. Here λ is
the wavelength of the source. ΔN is the number of rings counted.
• λ = (Δd x 2)/ ΔN is the formula for the wavelength of the sodium lamp. We take
two different set of readings to try and verify the fact that even if the shape of the
fringes are changed, the wavelength of the sodium lamp remains the same as
source is unchanged.
• The calculations for the 2 sets of data are shown in the following slides.
EXPERIMENTAL PROTOCOL
1) We place a white source of light and place a carboard with a small hole in front of it so
it acts as a point source of light
2) We setup the F-P interferometer and adjust the interferometer carefully to produce
clear white circular fringe in the centre.
3) We will setup the Michelson interferometer with the mirrors M1 and M2 perpendicular
to each other.
4) We change the fringe pattern using the fine micrometer and note the readings for
different coloured fringes.
DATA ANALYSIS
No of
fringes
d1 MSR
d1 VSR
d2 MSR
d2 VSR
d1(microm d2(microm
eter)
eter)
50
16
35
17
36
208.75
221.5
50
16
35
17
37
208.75
221.75
50
16
34
17
36
208.5
221.5
DATA ANALYSIS CONTINUED
• DISAPPEARENCE OF FRINGES
d1 MSR
d1 VSR
d2 MSR
d2 VSR
d1
d2
9
31
14
31
120.25
182.75
*d calculation:
d=(MSR*12.5)+(VSR*0.25)
DELTA LAMBDA CALCULATION:
Residual
LAMBDA
0,522
0,52
y = 0,04x
0,518
0,516
0,514
0,512
0,51
0,508
1 2 ,7
1 2 ,7 5
1 2 ,8
1 2 ,8 5
1 2 ,9
1 2 ,9 5
13
1 3 ,0 5
1
0,9
0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0
12,7 12,75 12,8 12,85 12,9 12,95
13
13,05
DELTA LAMBDA:
DELTA LAMBDA= 0.00213 micrometer
CONCLUSION
• First we tried the white light experiment but since it’s a very complicated experiment we
were not able to obtain the colourful fringes because white light has a very small
coherence length. So after trying for 1hr 30 mins we were told to do the basic
experiment
• So we optained delta lamda that is wavelength seperation of sodium lines as 0.00213
micrometer