Additional Info

• ID Code: P2-11
• Purpose: Demonstrate two-slit interference of single photons.
• Description:

  Collimated light from a laser diode is incident on a double slit, creating interference. A photomultiplier tube sensitive to single photons is attached to the rotating telescope of the spectroscope opposite the light source. The signals from the tube are seen on the oscilloscope and heard using an audio amplifier and loudspeaker.

  As the photon counter is slowly rotated the intensity of photons traces out the interference pattern for the double slit used. An identical slide on the Laser Cart (Demonstration M1-11) can be used to display the double slit interference pattern.

  The double slit used has slit width of 0.04mm and slit spacing of 0.250mm. With the single photon counter you can hear about nine interference maxima in the main diffraction maximum, pass through the diffraction minima on either side, and hear a few interference maxima in the second diffraction maximum, as seen in the photograph above.

• Availability: Available
• References: REFERENCES: (PIRA 7A55.20) See Demonstration Reference File for further information regarding this demonstration and its parts, including data on the single-photon counter and the slit.
• Loc codes: P2, ME2, ME3
• Videos-1: (simulation NOT video) Click here for an interactive computerized model of the double slit experiment produced at Kansas State University.