Featured in PASCO’s Advanced Physics Teacher Guide

Advanced Physics Teacher Guide


This manual features over 30 College Board curriculum and AP Physics exam inspired lab activities.

Interference & Diffraction

Lab Summary

Use a high sensitivity light sensor and a rotary motion sensor to determine the spacing between two slits on a slide with two very small closely spaced parallel slits.


Given a slide with two very small closely spaced parallel slits on it, students:

  • Employ a graphical method to experimentally determine the spacing between the two slits using the principles of diffraction and interference of light.
  • Use the mathematical relationship between slit spacing and the double-slit interference pattern maxima and minima to determine the spacing between two very small closely spaced parallel slits on a slide.


Students gain experience conducting the following procedures:

  • Determining that the only measurable quantities in the constructive interference fringe equation are the distance between interference maxima and the distance from the slit pattern to the viewing screen.
  • Producing a definite diffraction or interference pattern using a laser and double slit slide and pattern.
  • Measuring the distance from the central maximum to the first 5 closest bright fringes (constructive interference fringes).
  • Measuring the distance from the slit pattern to the viewing screen.
  • Plotting a graph of integer order m (1, 2, 3, 4, 5) versus constructive interference fringe distance (the relationship will be linear).
  • Using the slope of a best fit line to determine the slit spacing and compare that value to the actual value.

Sensors / Equipment Used:

PASPORT High Sensitivity Light Sensor


Designed to perform visible light studies from low intensity spectral studies to daylight. Built in oversampling reduces noise. PASPORT version.

PASPORT Rotary Motion Sensor


Put a new spin on many common experiments with this highly versatile sensor.

PASPORT Sensor Extension Cable


Allows an additional two meter length extension on all PASPORT sensors.

Aperture Bracket


With the Aperture Bracket, a student can vary the spatial resolution of the Light Sensor in six steps from 0.1 to 1.5 mm. Mounts to Basic Optics Bench.

Linear Translator -- Basic Optics


Used with the Rotary Motion Sensor and provides position data to the computer. Can be attached to Basic Optics Bench.

1.2 m Optics Track -- Basic Optics


The 1.2 m optics bench is a perfect length for investigations involving lenses, mirrors, and diffraction/interference patterns. Made of rugged extruded aluminum.

Precision Diffraction Slits


Includes two slit wheels allowing students to examine various diffraction patterns.

Red Diode Laser - Basic Optics


Designed to be used with Basic Optics System allowing students to explore interference patterns

The Associated Bundle:

Advanced Physics Standard Sensor Bundle


This bundle contains the probeware needed to perform all 37 lab activities in the Advanced Physics lab manual.

Interface Required

This experiment may require software and an interface for data collection.