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Fall 2009-Day 4
Diagnostic Questions

Diagnostic Question Document: reflection_dq.doc

Directions: Three students are looking at a covered mirror. A light source is to the left of the mirror. Student #1 is standing to the left of the mirror. The light source is between Student #1 and the mirror. Student #2 is standing directly in front of the mirror. Student #3 is standing to the right of the mirror.

If the mirror were to be uncovered, which of the students, if any, would see the reflection of the bulb in the mirror? Draw a sketch to represent your idea. Describe in words why you think what you think.

After the students had completed the diagnostic question, they had the opportunity to explore their ideas. Were their predictions correct? Why or why not?

The students explored where you can see an object within a mirror. Three students stood in front of a mirror. There was an object (a lamp) in front of the mirror also, but to the left. They were trying to figure out which student could see the image of the object in the mirror. They found that only one of them could see the lamp. Through exploration, they determined that the angle the light hit the mirror was the same angle that the light reflected back off of the mirror in the other direction. We later learned that these angles are called the angle of incidence (the going in angle) and the angle of reflection (the bouncing back angle). We further demonstrated this in class by quickly rolling a basketball against the wall. The ball bounced off the wall at the same angle that it was thrown against the wall.