PHYS 1400: PHYSICAL SCIENCE LAB LIBRARY

University of Central Arkansas, Department of Physics and Astronomy

Let the light warm up while you explain the procedure. Best results when the bulb has been on for about a half hour or so.
Align the light sensor with the center of the magnetic component holder from the optics kit. Position it at the end of the optics bench, lined up with the zero end of the measuring tape.
If you use the 0-600 lux setting on the light sensor, you cannot approach the source closer than about 12-15 cm without saturating and overloading it. If you use the 0-6000 lux setting, get as close as you like.
According to Vernier, it is possible to get perfect inverse-square results with their ($77.00) LED point source. Not so much with the light source in the blue optics kit. One option is to buy really expensive sources. Another option is to have the students plot a second, inverse-square curve for reference, and try to figure out why their curve does not precisely match it. A third option is to do a different lab entirely.

Lab Notes

Become familiar with units which describe the brightness or intensity of a light source
Measure the brightness of a point source as a function of distance
Prepare a graph to analyze the relationship mathematically
Compare the experimental plot to a predicted inverse-square graph
Examine the experimental set up and suggest possible improvements