Shadow Plots

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Fall 2009-Day 2
Light Activities
Playing With Shadows
Orientation to the Sky

What is a shadow plot?
We make shadow plots on a piece of sturdy file folder paper with a sheet of white paper taped on top. One end of a paper clip is bent and fastened to the middle edge of the white sheet of paper. When students set it flat on a ledge outside, a shadow is casted beyond the piece of the paper clip that is sticking up in the air.

What do shadow plots show?
We use shadow plots in Physics 111 to show how the orientation of the sun causes shadows to look different at different times of day. Students draw a dot at the end of the shadow that they see and record the time they do this. Over the course of one morning class session, students make several shadow plot observations from the same ledge location. Their instructor continues making observations during the afternoon. By examing the pattern of dots made through the end of the day, students are able to determine that the tips of the shadows change in a continuous, one-directional way. The direction of the shortest shadow is toward the North. They can see that shadow plots made near the equinox form approximately a straight line across the page. How might shadow plots made near a solistice appear?

Student Reflection: ”“Today we went outside to make sun dials and draw pictures of our shadows at the beginning of class. Every half an hour, we went back outside to add another point to our sun dials. I noticed that earlier on in the day, the sun seemed to move a significant amount, changing our shadows dramatically. As we got further into the day, closer to noon, our shadows for the sun dials changed less and less. The movement was not as significant. I suspect the opposite would be true as it got later in the day.”