481- BARON VOX WREDE ON THE ABSORPTION OF LIGHT 



A (cos i+ \/ — 1 . sin ?■) 



)1-^- ^ ^(co s2.^ + ./- l.sin2.^j ( 

 ^ l_^2/cos27r _ + a/- 1 .sin27r ^ j 3 



If in this expression, in which r is naturally less than 1, we suppose n 

 to be infinitely great, we shall have 



A (cos i + VZTi . sin i) 



=(1 - ^y " S 7 -^ zz: 2T\ V 



1 I -r°-/ cos 2 TT 1^ + v' - 1 . sin 2 TT -y- j t • 



By separating in this expression the real from the imaginary magni- 

 tudes we obtain 



A {\-rr-a (5) 



/ 1h \ 26 



cos e I 1 — r^ cos 2 tt — ) + ^- sin i sin 2 tt — - 



and 



/ 1h\ . . ^ lb 



sin I ( 1 — r- . cos 2 TT — J + r"- cos t . sin 2 tt — = 0. 



From the last expression we obtain 

 26 



r^ sin 2 TT , 



v/- 



2 r^ cos 2 r ^ + r* 

 \ 



and 



1 — r- cos 2 IT — - 

 A 



x/ 



1 - 2 r2 cos 2 TT — + r« 



A 



If we substitute this value of sin i and cos i in the formula (5) we have 

 after reduction 



(\-ry-a 



K= , (6)...* 



* / 1 — 2 ^- cos 2 TT — + r 



• Considering the partial reflection of a surface as a f offl^ reflection of all the 

 light in contact with the particles of the body, it is evident that, the form of the 

 particles being neglected, and the reflected part being called as before r a, i. e. 

 (1 — r) «, that part continuing in the original direction, the whole quantity r a 

 cannot return in a contrary direction, but that a part of the same must be re- 

 flected in different directions. To be convinced that such a change in the pre- 

 supposed hypothesis does not materially alter the results deduced from it, we 

 have only to suppose that the part of r a which is reflected in a contrary direction 

 is called r' a, as it is then evident that the intensities of the system of waves of 



