Can You See the Bike Shop Bell?

An Evening at the Bike Shop

Buses pass, neighbors walk dogs, and bicycle riders stop at a repair shop on a busy city street. The shop is planning an evening window display. Its owner, Imani, wants visitors to notice a bicycle bell. A science club helps her test a small model of the display before she arranges the real window.

The club puts the bell inside a covered test box. No outside light enters the box. A battery-powered lamp is the only light source inside. The bell does not make its own light. One marked opening lies between the lamp and bell. Another lies between the bell and a viewing hole. An observer looks through that hole. A shield keeps the lamp itself out of the observer’s view. Nobody looks directly into the lamp.

For each trial, the club follows the same steps. First, members set the lamp to on or off. Next, they leave both openings uncovered or cover one opening with the listed material. Each cover fits the whole opening, leaving no gaps around its edges. Finally, the observer reports whether the bell can be seen. The club records that result as yes or no.

The same lamp, bell, box, viewing hole, and observer are used throughout. Their positions stay the same. The club changes only the lamp setting or the covering listed in the table. The card is opaque: light cannot pass through it. The clean, clear plastic lets most light pass through. After testing, members draw models with arrows to show the direction light travels.