THE 



PHILOSOPHICAL MAGAZINE 



AND 



ANNALS OF PHILOSOPHY. 



[NEW SERIES.] 



DECEMBER 1827. 



LXV. On the Dispersio7i of Light, By M. Rudberg, of 



Stockholm.* 



T N investigating the principle, according to which, for the 

 *- explanation of the dispersion of light on the system of un- 

 dulations, we must suppose that when the light passes from 

 the air into a more refractive medium, the lengths of the 

 undulations are much contracted, in fact much shorter, — 1 have 

 found that the following relation appears to exist between the 

 length of the undulation of a certain colour in the air, and the 

 corresponding one in any other substance : 



'L = a.r; 



I being the length of the undulation in the air, and L that in 

 another substance ; and lastly, c, m two numbers which vary 

 only with the nature of the substance. 



I have taken the lengths of the undulations in the air as de- 

 termined by M. Fraunhofer, (Gilbert's Annals, 1823, p. 337) 

 viz. In the red, C = 0-00002422 of an inch. 



orange, D = 0-00002175 



green, E = 0-00001945 



blue, F = 0-00001794 



indigo, G = 0-00001587 



violet, H = 0-00001464 

 The lengths of the undulations in other substances being 

 always in the inverse ratio of the indices of refraction, I have 

 inserted them in the first column of each of the following tables, 

 according to the indices of refraction which M. Fraunhofer 

 has j)ublislied, in his Memoir on the determination of refrin- 

 gent and dispersive power (Schumacher's Astro?iomische Ab- 

 handlungen, 1823). 



* Communicated by the Author. 

 New Series. Vol. 2. No. 12. Dec. 1827. 3 F The 



