The angle found in part (a) is extraordinarily small (less than 1/50,000 of a degree), because the primary mirror is so large compared with the wavelength of light. Although diffraction is present at all aperture sizes, it becomes most pronounced with smaller apertures because a higher proportion of the total light striking. While it is true that the laws of physics and light waves mean that as the physical size of the aperture is made smaller, depth of field increases, diffraction. The on-axis gain is: G(0, 0) 4 2A (gain of uniformly illuminated aperture area A) Equation (11.1. Many novice photographers are confused by the fact that a small aperture has a large f-number or f/number, while a larger aperture has small f-number.
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