Diffraction Phenomena in the Focal Plane 



of a Telescope with Circular Aperture 



due to a Finite Source of Light. 



By 

 H. Nagaoka, Rigakuhakushi, 



Professor of Applied Mathematics, Imperial University, Tokyo. 



With Plate XYI-XV1Ï. 



The diffraction phenomena due to a circular aperture have for a 

 long time attracted the attention of physicists, on account of their 

 intimate connection with the theory of optical instruments. For a 

 point source of light, the problem has been treated by Airy, 1 * and by 

 Sch werd, 2 * and again by Lommel 3) , who has brought our knowledge 

 of if to the highest state of perfection as regards both Fraunhofers 

 and Fresnel's diffraction phenomena. For practical purposes, it 

 is necessary to modify the problem slightly, and investigate the 

 diffraction due to a finite source of light, and this has been done, in 

 connection with the resolving power or for the explanation of drop 

 formation during the transit of inferior planets, by Rayleigh, 4 André, 6) 

 Struve, 6) and Streb 1. 7) In spite of these investigations, the field of 

 research in this direction is far from being exhausted ; even the 



1) Airy, Camb. Phil. Trans. 5, 283. 1834. 



2) Schwere!, Beugungserscheinungen, Mannheim, 1830. 



3) Lommel, Abhandl. rf. bayer Akad., 15, 1884. 



4) Rayleigh, Wave Theory of Light, Encycl. Brit. 9th edition. 



5) André, Annales de l'École Normale, (2) 5, 275. 1876. 



6) Struve; Mémoires de l'Académie des Sciences de St. Petertbourg. 3d. 1882. 



Wied. Ann., 17. 1008. 1882. 



7) Strehl, Zeitschrift für Imtrumentenkunde, 15. 362. 1895. 



16. 257. 1896. 



17. 105. 1897. 



