Are these two light sources the same? Groups use a white card and a little cooking oil to create a photometer that allows for the comparison of two lights. The Inverse Square Law provides a way to calculate the actual difference in intensity of the lights.

Concepts

light, light bulbs, light intensity, luminosity, illumination, inverse square law, technology resources

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Instructional Ideas

• Take advantage of the opportunity to use the activity as an introduction to the Inverse Square Law
• Use the device to compare the difference between a new bulb and an old bulb

Classroom Considerations

• Position the device so that it does not get more ambient light on one side than another

Pros

• Provides a mathematical explanation of the relationship between the distances
• The video provides examples of what you should see along with directions on how to set up the activity

Cons

• The subscripts in the mathematical formula do not show up as subscripts