Here is a simple experiment you can run remotely or in person with basic household items: making a bat signal. First, have your students cut out a bat shape from black construction paper, then have them hold the bat in front of a desk lamp aimed at the wall. This setup looks like what we see in the movies and comics, but it doesn’t work! Instead of a projected bat shadow surrounded by a circle of light, we only see a slightly dimmer light projected onto the wall. With a little Socratic prodding, you can get your students to explore the basic principles of geometric optics to make functioning pinhole, pinpoint, and thin-lens bat signals.
The problem with the light–bat setup is that each point on the bulb acts as a light source that emits light rays in all directions. Portions of the bulb not blocked by the bat will...
