6D20.50 - Fraunhofer Diffraction
Demonstrate Fraunhofer diffraction.
Project the laser dot onto the wall and insert a ruling into the beam and rotate to show that the diffraction pattern rotates with the ruling. Then insert the second Ronchi ruling into the beam and align it so as to be parallel with the first ruling. Once again, a single diffraction pattern is seen. But if you now rotate one of the rulings so the angle between the rulings goes from 0-90° you get an increasingly complex pattern until you get t he Fraunhofer pattern for a square when you reach 90°. A third ruling can be added so even more complex Fraunhofer patterns can be shown. One can also show the difference between the 300 and 500 L.P.I. gratings or a combination of the two.