Inverse Square Law
Safety Warnings
Warning: Light Source Heat
Purpose
A point light source casts the shadow of a small square barrier onto a gridded board. Each time the barrier-to-source distance is halved, the shadow area quadruples — directly visualizing the inverse square law. Students see the geometric origin of the \(1/r^2\) dependence common to light intensity, gravity, and Coulomb's law.
Figure 1:
Barrier at maximum distance from the light source. The shadow on the gridded board covers approximately one grid square.
Figure 2:
Barrier moved closer — shadow covers approximately 4 grid squares (2x2).
Figure 3:
Barrier at half the original distance — shadow area has quadrupled.
Figure 4:
Barrier at minimum distance — shadow covers approximately 16 grid squares (4x4), sixteen times the original area.
Equipment
- 1
- 1