Missing Arago Spot


  • This demo is meant to illustrate what would happen if photons behaved like classical particles, or bb’s.
  • Bb’s act as photons, and circular platform acts as a “light” barrier.
  • With paper and carbon paper under the platform, pour the bb’s onto the platform. BB’s will scatter off and make marks on the paper underneath the platform where they hit. Spoiler alert: They don’t make an Arago spot.
  • Use funnel to obtain uniformly vertical stream.
  • Copper sheet provides hard, low-bounce surface. Long cardboard box, located next to demo, in L01, can be used to prevent scattering of bb’s across table surface.
  • Demo Located in L01, section C1.