• An expanded laser beam produces a spot in the center of the shadow of a 4 mm sphere.
  • Can be projected on to a screen or whiteboard in a dark room.
  • The spot will be visible from ~20 cm and beyond.

  • View seen by students in darkened room.

        (put laser at end of optics bench, front end should be at ~380 mm)
        (make collimated beam with 18 mm lens at 440 mm, .04 or .08 mm aperture at 458 mm, 252 mm lens at 700 mm)
        (fine tune position of aperture using index card in front of 252 mm lens)
        (put sphere at 1000 mm)

  • Version 2

        (make expanded beam with -22 mm lens)