Practice of pinhole imaging

Mozi is very good at optics, and gives a wonderful description of the linear propagation of light, the reflection of light and the imaging of some objects.

Once, Mozi did an optical experiment. He stood alone outside the room, facing the small hole where the sun rose. Under the sunlight, an inverted portrait appeared on the wall opposite the room. Through the optical experiment of pinhole imaging, Mozi expounded the principle of straight-line propagation of light: that is, light shines directly from top to bottom, and people's heads and feet form reflections on the upper and lower sides, becoming the forerunner of photographic technology in later generations. The cameras and video cameras we use now are a step forward on the basis of Mozi's research and invention.

Pinhole imaging

(1) Put a piece of white paper on the desktop as a screen, put a cardboard with a small hole between the incandescent lamp and the light screen, and fix it on the bracket.

(2) Turn on the light switch, and you can see the image of the filament on the light screen. The opening of the image is opposite to the opening of the filament, indicating that the image is upside down, as shown in the figure. If the position of the small hole moves up and down, the size of the image can be changed.

(3) If the holes are changed into small squares, rectangles and triangles respectively, their imaging will remain unchanged, indicating that the imaging of the holes has nothing to do with the shape of the holes.