SCIENTIFIC MEMOIRS. 



VOL. L— PART IV. 



Article XXV. continued. 



Attempt to explain the Absorption of Light according to the 

 Undulatory Theory; by Baron Fabian von Wrede. 



From PoggendorfF's Annalen, vol. xxxiii. Nos. 23, 24 and 25. 



J.N order to find its intensity A, I multiply the equation (2) by 



v' — 1 and add it to the equation (1); I then obtain 



A (cos i + V — 1 . sin i) 



f / 2i , , . 2b\ 



= (1 — r)- a -; 1 + r- \ cos 2n y + V— l'Sm27r -r- I 



+ r^(cos2.2Tr~. + ^^"i ,siu 2.2 7r |- j 



, 2«/ « 26 , , . ^ 2^»\) 



+ r J cos M . 2 IT -— + V — 1 . sin M.2 ^ -y j j ; 



or, since 



cos mz -\- V — 1 . sin m z = (cos z + ^f — \ . s\n z) 

 A (cos I + v' — 1 • sin j) 



= (1 - rya { 1 + r"- (cos 2 tt ^ + ^~1 .sin2,r^) 



/ ^ 26 , / . 2b\„ 



+ r<(cos27r— + V - 1 .sin27r y) + 



....+r'" (cos2 7r|^+ ^/~r:sin2 7r|^y'. 



This is a geometrical series, by the summation of which we obtain 

 Vol. I.— Paht IV 2 i. 



