# Fall 2016 Day 3

Peer Instructor Reflections

Generating a Question about the Moon
Written by: Katie Rodriggs

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Developing and Using Mathematical Representations to Estimate the Diameter of the Sun
Written by: Nathalie Gaebe

I started the activity by letting the group know that the goal of our next activity was to measure the diameter/width of the sun using a pinhole. Each group was given a white sheet of paper, a meter stick and a sheet of paper with a foil in the middle and a pin hole in the foil. We took a field trip outside. The sheet with the pinhole was held facing the sun with the white sheet behind it. The meter stick was held between the two sheets of paper with each end touching one sheet of paper. Once the groups saw the projection of the sun on their white sheet of paper, they traced the outline of that projection.

Once back inside, we had each group draw the ray diagram of the sun, the pinhole, the projection and the meter stick. We asked them how they thought that they could find the width of the sun with the information that they had. Some groups mentioned ways to find the width using ratios and proportions. They measured the width of the projection to be 1 cm and the distance from the pinhole to the projection was 1 m. The distance from the sun to the pinhole is 100,000,000 mi. Using this information, groups all had the idea to set up a proportion to solve for the width of the sun. We then discussed how we can use proportions because of the similar triangles created by the light rays traveling in straight lines through the pinhole from the sun to the projection.

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