Tutorial details

There are many observations throughout this tutorial. It is important that students make predictions before viewing the corresponding demonstrations.

Section I: Point sources of light

In Questions A-D, students predict what will appear on the screen when a mask with a circular hole is placed between a bulb and the screen. They consider how moving the bulb or introducing a second bulb would affect the appearance of the screen, which builds to the idea that light travels in straight lines.

In Questions E-G, students consider the effect of replacing the circular hole with a triangular one as well as the impact of moving the bulb farther and farther away from the mask.

Section II: Extended sources of light

In Questions A-C, the circular hole is again used and bulbs are continually added in a vertical stack. This leads to the long filament bulb, where students recognize that it can be treated as a collection of many closely-spaced bulbs.

Questions D-F involve variations on the experiment with the long filament bulb. Students then consider a frosted bulb in Question G.

Section III: Shadows

In this section, students apply their understanding in the complementary context of shadows.

Section IV: Supplement

Students make quantitative predictions about the size of the image produced by light from a small bulb passing through a small hole. They also examine the effect of halving the diameter of the hole in the mask for both the small bulb and a long-filament bulb.

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Discussion