Dr. Ezrailson: Light, Brightness and Distance
I greatly appreciated the pre-lab instructional introduction. It was a good reminder of the relationship of intensity to distance. That inverse relationship, I=P/Area should have been verified by experimental results.
Preliminary Questions
The power passing through the inner sphere should be greater than the power through the
outer sphere. The surface area of the larger sphere sould be exponentially larger than the surface area of the smaller sphere, so the intensity will be inversely proportional to 4X the distance (r) squared, reduced much faster in the larger sphere.
Analysis
A natural log graph with our data should have yielded te graph & equation of a line with the coefficient (slope) of X being the power of r in the intensity equation. Our data deviated more than necessary, following an inverse function but not inverse square function. This deviation could have been effected by several errors. It was hard to measure the position of the light sensor until we followed the suggestion of another lab group which helped us allign the light source and measure on the same level. There were probable intensity misreads. I did not read through the procedures before starting & did not wait for intensity values displayed to stop changing before a "keep". Finally, we had conputer problems so we did not take/have time to rerun the lab in a dark room--which would have produced better intensity data. I appreciated this lab in its entirety! After thinking of the analysis I needed for this blog comment, I realized I refreshed and learned a lot. This equipment and this lab's sections & extensions promote principle learning and good math & computer practice for students.