Shape of the F at the wall of the camera obscura

This animation is part of my presentation at the Second International Prof. Dr. Fuat Sezgin Symposium on the History of Science in Islam in Istanbul. More information will become available at my website: Ibn al-Haytham and his apparatus for the observation of light. One of the museum object is a model of a camera obscura. The model uses a halogen lamp that produces divergent light. A halogen lamp close to the object, being a letter F cut out from a metal sheet, has different properties than sunlight. The animation focuses on the image of the F at the outside of the camera obscura. One might expect an inverted F or a right-standing F, but what about something oval? The purpose of the animation is to show what happens when we consider all the rays from all the points. A description of its interface is below the animation.
This animation shows the shape of the letter F on the outer wall of the camera obscura. It does not provide its shape inside the camera obscura.
  • A point is moving along a spiral in the halogen light. Rays will be drawn from hundreds of points on this spiral. Click on animation to start and stop the animation. The animation counter displays its progress. This counter is display only.
  • Select the right speed for your animation.
  • One may widen or narrow the F to investigate its effect on the shape on the wall.
  • Click in the 3D window for a toolbar to pan your view
  • A reset button is available in the topright corner.
The animation has two modes.
  • show all rays originating from a specific point at the spiral
  • show single ray in a point-by-point approach from the specific point at the spiral to each individual point on the F.
The animation also shows the image of the frame on the wall. Outside the contourline of that frame, light of the halogen lamp falls directly on the wall. As a result of the large size of the halogen lamp, both areas overlap. That is why one will not observe a sharp shadow of the frame on the wall.In case all rays are shown, one sees the image of the F moving on the wall. Increase animation speed for fast results. All images are stacked on each other, like summing up all the points. In case of a single ray, that ray is emphasized. Each hit in the wall is made visible by a single spot. All the spots together create the final image of the letter F at the outer wall of the camera obscura. Reduce animation speed to see that the rays follow a sequential grid on the letter F.

Museum Catalog

Museum Catalog
illustration is from the museum catalog: book 3, chapter 6, Optics (page 182)
Image

YouTube: Fast version

YouTube: medium speed version