With college bowl season in full swing and the NFL regular season wrapping up, it’s an exciting week for pigskin fans. In modern football stadiums, the lights go all around the rim of the stadium and there are practically no shadows on the field. In smaller or older stadiums, however, there are only a few banks of lights and each player has several indistinct shadows springing from their feet. This is a demonstration of the penumbra effect. A penumbra is an area of partial shade that occurs when light does not come from a single point.
Students can explore these partial shadows with the Penumbra Effect Gizmo. In the Gizmo, students manipulate the number of light sources, spacing of light sources, and width and distance of a shadow block. They can then use ray traces to determine how much light is reaching each part of the penumbral shadow. These concepts can then be applied to the understanding of total and partial eclipses using the 2D Eclipse or Eclipse Gizmos.
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