Pinhole Projection
Safety Warnings
Warning: Hot Lamp Surface
Warning: Electrical Safety
Purpose
Multiple pinholes in aluminum foil each project an independent inverted image of a lamp filament, demonstrating rectilinear propagation. A large converging lens then collects all pinhole images into a single bright focus, showing the light-gathering advantage of lenses over pinholes.
Figure 1:
Multiple pinhole projections of the lamp filament on the screen. Each pinhole produces its own inverted image of the filament.
Figure 2:
The large converging lens focuses light from all pinholes to a single bright point. Chromatic aberration is visible as color fringes around the focus.
Figure 3:
Full apparatus: variac, lamp with aluminum tube shield, white poster board screen on the blackboard, aluminum foil, and push pins.
Figure 4:
Close-up of the aluminum foil pinhole array covering the lamp tube end. Push pins are used to punch holes of varying sizes.
Equipment
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