Make a lightproof box with a tiny hole on one side and a translucent screen on the other to project an inverted real image of the outside scene. This hands-on build demonstrates how light travels in straight lines and why small apertures produce sharper images.

1. Gather materials: shoebox with lid, aluminum foil, white parchment or tracing paper (or thin white plastic), scissors or craft knife, pin or needle, black tape, and black paint or dark paper.
2. Darken the box interior by painting it black or lining it with dark paper to reduce internal reflections; let dry if painted.
3. Cut a square window (about 6–8 cm per side) in one short end of the box; tape parchment or tracing paper over this opening to make a viewing screen pulled flat without wrinkles.
4. On the opposite end, cut a smaller opening (about 2–3 cm per side); cover it with a piece of aluminum foil taped tightly around the edges.
5. Using a pin, make a single clean hole at the center of the foil (start tiny; you can enlarge later). Aim for a circular hole with smooth edges.
6. Close the box securely so no stray light enters except through the pinhole; seal seams with black tape if needed.
7. Point the pinhole toward a bright scene (a window or outdoor landscape) and look at the tracing-paper screen; allow your eyes to adapt. You should see a dim, inverted image of the scene.
8. Adjust for sharpness and brightness: try smaller or larger pinholes on fresh foil patches, move the box closer to or farther from the scene, and shade the screen from stray light to improve contrast.

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• Replace the tracing paper with wax paper or thin white plastic to compare image brightness and contrast.
• Mount the screen on a sliding inner sleeve (second box) to change the distance from pinhole to screen and observe the effect on magnification.
• Use photographic paper or a phone camera placed at the screen to record a long-exposure pinhole photograph in bright daylight.
• Make a room-sized camera obscura by darkening a room and placing foil with a pinhole over a small window opening.

• Use scissors or craft knives carefully; adult supervision recommended for cutting cardboard and foil.
• Pins and needles are sharp; handle with care and store safely after use.
• Never aim the pinhole camera at the Sun or bright reflections and never look at the Sun through any viewer; permanent eye damage can occur.
• Keep liquids, paints, and adhesives away from eyes and mouth; use in a ventilated area and wash hands after the build.

• Why is the image upside down on the screen? (Light travels in straight lines; rays from the top of the scene pass through the pinhole and land at the bottom of the screen, and vice versa.)
• What happens when you make the pinhole larger or smaller? (Larger increases brightness but causes blur from overlapping light cones; smaller increases sharpness but dims the image and can introduce diffraction if too small.)
• How does the distance between the pinhole and the screen affect the image? (Greater distance increases image size but reduces brightness; smaller distance does the opposite.)
• Why do pinhole cameras have effectively infinite depth of field? (Each scene point maps to a tiny region regardless of distance because focusing is set by geometry of the pinhole, not by a lens.)
• How do lenses improve on pinhole cameras? (They allow a large aperture to gather more light while focusing rays to points on the image plane, enabling shorter exposures with controlled depth of field.)