We disagree with the exclusion of Newton's laws, Ohm's law and the energy conservation law from physics of primary schools in the Czech Republic!

Study of light diffraction
(Diffraction on the 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 from the positions of the diffraction maxima determine the lattice constant of the optical lattice used.

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

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

Measurement procedure

  1. We're running a remote DiANE experiment. Wait for the calibration of the apparatus (about 15 sec)

  2. We can see the diffraction patterns of the optical grating for the individual colours of the lasers used on the webcam. Switching lasers is done by selecting the item in the experiment control panel (see description of controls).

  3. We obtain the entire 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 colour laser again, the data series will be deleted!

  6. We follow the same procedure for the blue and green lasers.

  7. We will exit the remote task after measuring the required number of data (and saving all the 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 scattered light (in degrees) on a graph.

  10. We check that the zero-order maximum actually corresponds to 0°, otherwise 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 grid constant of the grid used 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 remaining laser colours, except that we already know the lattice constant and from expression (3) we obtain the wavelength λ of the laser used.