Which principle was applied in Alhazen's camera obscura experiments to demonstrate rectilinear propagation of light?

💡 Explanation

When light passes through a small hole in the camera obscura, diffraction occurs because the aperture size is comparable to the wavelength of light, resulting in a projected image according to rectilinear propagation observed even for short propagation distances. Therefore diffraction is key, rather than refraction, interference or reflection which depend on distinct properties or interfaces.

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