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Study of diffraction phenomena
(Diffraction on a grating)

Work Task and Measurement Procedure

Work task:

  1. Measure the diffraction pattern on the grating with a red laser (λ = 650 nm). Plot the diffraction pattern (the dependence of the light intensity on the angle of the scattered light).

  2. Qualitatively compare the obtained diffraction pattern with the theory and determine the lattice constant of the optical lattice used from the positions of the diffraction maxima.

  3. Similar to point 1, measure the diffraction on the same grating using only a blue (green) laser. Plot the diffraction patterns obtained and compare them with each other and with the red laser pattern (again, discuss agreement with theory).

  4. From the positions of the diffraction maxima of the blue (green) laser diffraction pattern, determine the wavelengths of the lasers used. Compare the wavelength values obtained with the corresponding colors from the light spectrum.

Measurement Procedure

  1. We're doing a remote DiANE experiment. Waiting for the calibration of the instrument (about 15 sec)

  2. On the webcam we can see the diffraction patterns of the optical grating for each color of the lasers used. Switching the lasers is done by selecting the item in the experiment control panel (see the description of the controls).

  3. We obtain the whole diffraction pattern for the red laser by successively measuring sections of the diffraction pattern.

  4. We continuously check the measured values in the graph and, if necessary, stop the measurement and start again from the beginning.

  5. We save the complete measured diffraction pattern – if you start measuring the same color laser again, the data series will be deleted!

  6. Do the same for the blue and green lasers.

  7. We quit the remote task after measuring the required number of data (and saving all experimental value files!).

  8. We open the selected experimental data set in a spreadsheet.

  9. We plot the dependence of the light intensity (in relative units) on the angle of the scattered light (in degrees).

  10. We check that the zero order maximum is indeed 0°, otherwise we correct for systematic deviation.

  11. We determine the angles at which the 1st, 2nd … order maxima occur.

  12. We determine the value of the corresponding grating constant of the used grating according to formula (3) (can be used for individual orders of maxima and the resulting value determined as an average value).

  13. We proceed similarly for the other laser colors, except that we already know the grating constant and from expression (3) we obtain the wavelength λ of the laser used.