# Day 138: Light Intensity vs. Distance

*College-Prep Physics:* Students designed a lab to determine the relationship between light intensity and distance. But first in the pre-lab, they made observations about moving the light, the square hole, and the grid paper. Then they had to invent a “light intensity factor” much like they had to invent the “cheesiness index” the other day. Finally, we agreed upon a common factor for us to all use in the lab: light intensity = # light bulbs / light area. This was similar to cheesiness = # bags of cheese / pizza area. The handout is here. The graph and analysis they had to do was identical to the math relationships we analyzed yesterday.

*Conceptual Physics:* Students used the bike generators and a diode to charge a rechargable NiCd battery. They pedaled for 20 minutes, stopping to take a battery voltage reading every 5 minutes.