Laurence, Lionel · London, School of Optics · leaf 346
ed from L to enter the telescope and give riseto a sharp image therein. With a cyl. the image will be a line; with a sph.- 334 GENERAL AND PRACTICAL OPTICS cyl. there will be two line images at different distances. As in other tests,a known sph. must be added, if the unknown lens is too strong, too… … Fig.: 350. Another method. Light from the pinhole P is brought to a focus at Aby D, a Cx. lens. A is marked. The telescope T adjusted for oo is placeda convenient distance behind A. The lens L to be measured is then introducedbetween T and D and moved about until the image of P is seen sharply.…
Optics
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