Why Is Alaska So Cool?
(When the days are so long?)

A Series of Math and Science
Investigations in Sunlight Intensity
using Excel, Graphing Calculators and CBLs

Activity 6: Distance Intensity Investigator

Investigations in Light Intensity Change over Distance

Guiding Question:	How does the intensity of light change as the distance from the light source increases?
Description:	Students perform an experiment using a CBL light probe and TI-83 calculator to measure the light intensity from a source at increasing distances from the source. The students then plot the data and fit a several types of regression equations to it (polynomial regressions of degree 3 and 4 and a power regression) in the TI-83 and Excel. Students should discover that the relationship of the intensity varies inversely as the square of the distance.
Objective:	After completing this lesson, a student should be able to analyze light intensity striking a surface at varying distances from the light source.
Teaching Strategies:	Students should work in pairs to perform the experiment. The student will need the program called BULB loaded into their calculator. The program can be downloaded using TI-Graph Link.
Assessment:	Concluding questions are provided to measure a student’s ability to find data points on the graph, to predict new values not in the original set, and to decide which type of regression equation best models the data.
Download:	Lesson Plans Concluding Questions Answers to Concluding Questions Sample Data Excel Graph BULB program