Tables 204-205. 

 OPTICAL CONSTANTS OF METALS. 



TABLE 204. 



195 



Two constants are required to characterize a metal optically, the refractive index, n, and the 

 absorption index, k, the latter of which has the following significance: the amplitude of a wave 

 after travelling one wave-length, A^ measured in the metal, is reduced in the ratio' i :e — ^^^ or for 



any distance d, i : e — ^. for the same wave-length measured in air this ratio becomes i : e jy. 



itk is sometimes called the extinction coefficient. Plane polarized light reflected from a polished 



metal surface is in general elliptically polarized because of the relative change in phase between 



the two rectangular components vibrating in and perpendicular to the plane of incidence. P'or a 



certain angle, (princii)al incidence) the change is 90° and if the plane polarized incident beam 



has a certain azimuth ^ (Principal azimuth) circularly polarized light results. Approximately, 



(Urude, Annalen der Physik, 36, p. 546, 1889), 



_ , „- , , sin A tan a , , , „_^ 



k = tan 2^ (i — cot %) and n ^ , . .^^ (1 + 2 cot^,;,). 



For rougher approximations the factor in parentheses may be omitted. R = computed per- 

 centage reflection. 



TABLE 205. 



(The points have been so selected that a smooth curve drawn through them very closely indicates the characteristics 

 of the metal.) 



Drude, Annalen der Physik und Chemie, 39, p. 4S1, 1890; 42, p. 186, 1891 ; 64, p. 159, 1S98. Minor, Annalen 

 der Physik, to, p. 581, 1903. Tool, Physical Review, 31, p. i, 1910. Ingersoll, Astrophysical Journal, 32, p. 265, 

 1910; Forsterling and Fr^edericksz, Annalen der Physik, 40, p. 201, 1913. 



Snuthsonian Tables. 



