Diameter of the Sun

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Fall 2009- Day 3
Sun Earth Moon System Phenomena

pinholewithsun.jpgThe students extended their exploration of the pinhole phenomena by observing the sun. Small groups of students went outside with a meter stick, a piece of cardboard with a hole in it, and a white piece of paper attached to a wooden board. The students oriented their cardboard with a hole in it so that sun light traveled through the hole and ended up appearing about one meter away on the white piece of paper that the students were holding up.

Using the image of the sun and the mathematical information they already had, the students worked in small groups and developed a formula for determining the diameter of the sun. Formula: Diameter of sun/ distance of sun from pinhole = diameter of image/ distance of image from pinhole.
-First, they made sure that the distance between the cardboard with the hole and the white piece of paper was about 1 meter.

-Next, they measured the diameter of the image of light that appeared on the white paper. (About 1 cm.) They were also told how far away the sun was from earth. (About 100 million miles)

-Then, they drew a picture to help them conceptualize the geometrical processes that were occurring. Their pictures looked similar to the pictures they had drawn in previous days to explain pinhole phenomena. They included light traveling in straight lines through a pinhole and ending up at an image of the original light source.

-Then, by inserting the numbers they already had onto their pictures, they devised a formula for determining the number that they did not know (the diameter of the sun).

-Finally, by using basic algebra skills, students determined the only variable they did not know (the diameter of the sun). They found that the diameter of the sun must be about 1 million miles.

-Afterward, the small groups of students presented their white board findings to the other groups in class. Their white boards included information such as ray diagrams, predictions, comparisons with observations, powerful ideas about light, etc.

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