In this experiment designed for use with PASCO Capstone software, the student measures intensity as a function of distance from a point of source and from an extended (5 cm x 5 cm) source. Manipulations of a computer model verifies that for the point source, the intensity drops off like an inverse square. But for extended source, the data cannot be fir by an inverse square relationship.
As the student slides the light sensor away from the Light Source, the Optics Track keeps everything aligned. The Rotary Motion Sensor measures the position, allowing the intensity vs. distance graph to be plotted in real-time. Students immediately see the relationship between distance and intensity of light.