Preston, Thomas, Joly, Charles Jasper, 1864-1906, Parsons, John Herbert, Sir, 1868-1957, donor, University College, London. Library Services · London : Macmillan and Co. · leaf 128
hich refracts to a point the light diverging from another point is called an aplanatic surface, and the points are called conjugate foci with respect to it. The fundamental relation connecting conjugate foci 0 and 0' is that the time of propagation is the same along all the paths by which the light… … Fig. 58.— Aplanatic Lens. verging to 0'. Every point of this wave is a pole with respect to 0', and all the disturbances which simultaneously reach 0' are in the same phase. The illumination at 0' is consequently very intense. At points outside the cone OAB there is destructive interference and…
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