ISSN:
1476-4687
Source:
Nature Archives 1869 - 2009
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
Notes:
[Auszug] Any lens with spherical surfaces may be used as a double focus lens, by making use of the second focus formed by light reflected internally at the lens surfaces. The focal power of a weak bispherical spectacle trial case lens is about seven times as great as the marked power for this doubly ...
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1038/218942a0