Refraction: Cup and Dot Experiment

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Fall 2009-Day 7
Reflection and Refraction Light Activities

Today, the students got to explore the physics phenomena of refraction. This activity was exciting because the students got to see and do the experiment themselves. Each group was given an empty cup that had a dot inside of it. The dot was above the halfway mark on the cup, but not too close to the top. One person in each group got down at eye level with the cup. Those group members were told to find the dot inside the cup and then lower their eyes just slightly to where they could not see the dot anymore. Their partners then filled the cup with water. The water line ended up being above the dot by a little bit. The partners who had been at eye level with the cup were amazed at what they saw. Once the water had been poured into the cup, the dot was then visible to them! They wondered how this was happening. The other group members took turns observing this phenomena, which they later learned was called “refraction.” On their white boards, students tried to draw and explain what was happening. It took them a while to figure out, but the students realized that some of the light rays travelled through the water to the dot, then bounced in all directions, some of which travelled straight to the surface of the water where the light rays bent and travelled through the air to the students' eyes.

These whiteboard drawings demonstrate students' ideas as they began processing the scientific phenomena of refraction. Although they are headed in the right direction, there are nuances that need further discussion, such as the need for a straight line from the eye back to the “image” of the dot.

This whiteboard drawing demonstrates further understanding of refraction because a straight line is drawn from the image of the dot to the figure's eye.