TABLES 204-205. 



OPTICAL CONSTANTS OF METALS. 

 TABLE 204. 



'95 



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

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

 after travelling one wave-length, A. 1 measured in the metal, is reduced in the ratio 1 I :e 2Jrk or for 



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

 nk 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. For a 

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

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

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



k = tan 2 (i cot 2 ) and n = 



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.) 



