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Spherical Aberration

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-472

2025-12-20

436

In order that the results mentioned in the preceding discussion on lenses may be obtained experimentally the lenses must be thin and the aperture small. If a thick convex spherical lens is used, the rays that pass through it near the edge do not focus at the same point as those that pass through near the middle of the lens.

This can be shown by construction as in Fig. 1. The rays LA come to a focus at P, and only those rays quite near the center focus at C. The effect of this is to make the outside of the image indistinct when the center is distinct, and vice versa. This defect may be remedied by using a diaphragm with a hole in it, in front of the lens, as DD'. This makes the image more distinct, but as it cuts off the light from the outside, the image is not so bright.