How can we find minimum deviation using aspectrometer ?

Asked by  | 21st May, 2009, 01:26: PM

Expert Answer:


for measuring the angle of minimum deviation using spectrometer, steps given are followed.



1. Remove the prism from the spectrometer and align the telescope so that you can see the illuminated

slit in the cross-hairs of the telescope. Adjust the focus on the telescope if necessary.

2. Record the telescope angle and label it theta0

3. Replace the prism. Using the unaided eye (no telescope),locate the image of the atomic spectrum. Narrow the slit as much as you can while still keeping thespectrum visible.

4. Gently rotate the prism back and forth. As you attempt to make the deviation angle smaller, the

spectrum should appear to migrate in one direction until a point at which it reverses direction and

migrates back to where it came from. Position the prism so that it is roughly at the reversal point.

5. Position the telescope so that you can view the spectrum when the prism is oriented at the reversal

point. Make fine adjustments to the prism orientation so as to precisely pin down the reversal point.

6. Locate and record the telescope angles thetha (lambda)

7. Calculate the angles of minimum deviation thetha

for the different wavelengths.thetham (lambda) according to the equation

thetham(lambda) = thetha(lambda)− thetha0


Answered by  | 30th May, 2009, 12:52: PM

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