Make an image with a pinhole
Before you begin: A cardboard box, tracing paper, foil and a tiny pre-made hole. Use an ordinary bright room scene, never the Sun.
A pinhole admits narrow bundles of light from each part of a scene. Light from the top of the scene reaches the lower part of the screen, making an inverted image. Unlike a lens, the hole does not focus by refraction.
Hole size is a tradeoff: a large hole admits more light but mixes rays from nearby scene points; an extremely small hole introduces diffraction and becomes dim. Start with a visible image rather than chasing a supposedly perfect hole.
Worked example & observations
Original tabletop experiment: put tracing paper over one end of a light-tight box and the small foil opening at the other. Point it at a bright window frame, keeping the Sun outside the view. Shade the viewing screen. Record whether the frame is inverted. If you double the hole-to-screen distance with the same view, the image becomes approximately twice as large, though dimmer.
Your turn
A 3 cm-tall projected shape appears with a 10 cm hole-to-screen distance. Predict its height at 20 cm if the distant scene and viewing direction remain fixed.
Show answer and reasoning
Approximately 6 cm by similar triangles: 3 × 20/10. This geometric model does not predict brightness or sharpness, and a nearby subject makes the fixed-scene assumption more important.
Watch for: Light leaks can wash out the image. Seal the box before enlarging the hole. Never use the assembly to view the Sun or a laser.
Published and planned
Published: this starter lesson, worked example and exercise with an answer.
Planned: Documented pinhole builds, prism experiments and contributed optical contraptions.
Validation: source review and mathematical checks where applicable. Photography captures, audio listening and device workflows have not been performed for these lessons. Synthetic cases are labelled; no personal media or field observations are implied.
References
Original AUWEN teaching and examples. Sources reviewed 14 September 2026.
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