Light & Optics: Inverse Square Law

Explore the relationship between the intensity of light and the distance from the light source.

Lab Summary:

Students will use a Light Sensor to investigate the inverse square law. Students will measure the intensity of a light source as the distance between the sensor and the light source is increased. They will examine the shape of the graph and determine how the intensity of light is related to the distance.

Download free labs:

(student versions)

Computer-based lab (PDF, 480 KB)

Xplorer GLX-based lab (PDF, 2.2 MB)

Method:

Use a Light Sensor to measure the light intensity from a small light source as the distance of the sensor from the source increases. Examine the graph of light intensity versus distance and versus distance squared to determine the relationship that best fits the data.

Here's What You Need:

Required for computer-based lab:

(See lab download for Xplorer GLX-based lab requirements, which may differ)

Probeware

• PASPORT Light Sensor (PS-2106A)
• Xplorer GLX Graphing Datalogger (PS-2002)
  (or alternate PASPORT interface -- see other options)

Other Materials

• Basic Optics System (OS-8515C)
• Aperture Bracket (for Basic Optics) (OS-8534A)

Lab Manual:

The computer-based activity is included in Explorations in Physics (PS-2810). The Xplorer GLX-based lab is included in Physics with the Xplorer GLX (PS-2826). Both manuals are complete with Teacher Information pages, student instructions and handouts, and sample data.

For your convenience, we offer bundles which provide the probeware for the activities in the manual. For more, please see:
Computer-based Physics Lab Manual and Bundles
Xplorer GLX-based Physics Lab Manual and Bundles