6C20.30  PINHOLE DIFFRACTION



  • A divergent laser beam passing through an iris diaphragm forms a dark spot in the middle when the iris is stopped down.
  • Can be projected on to a screen or whiteboard in a dark room.
  • The spot will be visible from ~1/2 m and beyond.


  • View seen by students in darkened room.




        (put laser at end of optics bench, front end should be at ~380 mm)
        (make divergent beam with 18 mm lens at 440 mm, aperture at 460 mm, 252 mm lens at ~510 mm)
        (put pinhole at ~550 mm)

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