The theory of ocular defects and of spectacles / translated from the German of Hermann Scheffler by Robert Brudenell Carter with prefatory notes and a chapter of practical instructions.
- Hermann Scheffler
- Date:
- 1869
Licence: Public Domain Mark
Credit: The theory of ocular defects and of spectacles / translated from the German of Hermann Scheffler by Robert Brudenell Carter with prefatory notes and a chapter of practical instructions. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![Then ^ ^ ^ sin. s p q ^ f since these are the angles of sin. OPq' sin. spq' 1 incidence and refraction. But, in the triangles P o Q, p 0 q', p Q . a . sin. p 0 Q =— sin. 0 p Q = . sin. o p Q, QO . a + r' sin. p 0 q'= -- sin. o p q'= sin. o p q': q'o a' + r' Whence, since the angles p o Q, p o q' are the same, we have a . a! . , -. sin. 0 p Q = sm. 0 P Q ; a + '/• a + r Then let the ray q' p p' be refracted from the lens at p' in the second surface; it will pass out of the glass with an index of retraction — ; let it meet the axis in q. n Let p' q= b q = X; o' q= x r; o' qj — a' — r, since the thickness of the lens is supposed small. It may be shown, by the same steps as in the former case, that 1 a' ^ • or 71 cl' — 1' X r n a' — r a; + r ’ d x Hence, by adding [a] and [6] together, we have This expression, though found for a bi-convex lens, is per-](https://iiif.wellcomecollection.org/image/b2236397x_0016.jp2/full/800%2C/0/default.jpg)
