Die theoretische Grenze für die Leistungsfähigkeit der Mikroskope. (The Theoretical Limit of the Efficiency of Microscopes).

Leipzig, J.A. Barth, 1874. Without wrappers. In ""Annalen der Physik und Chemie. Hrsg. von J.C. Poggendorff"", Jubelband. With titlepage to ""Jubelband"". Titlepage with a stamp. Pp. 557-584

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First appearance of a fundamental paper in modern optics in which Helmholtz published his discovery of the resolution limit of the microscope. He found that the limit for the difference of magnitude that we are able to distinguish plainly is in general found equal to half the wave-lenght of theparticular light employed. A further increase in optical power beyond that of the best modern instruments does not therefore seem possible.