'>1-'^ H. XACJAOKA. 



Tlu'VcCorc, l)_v lorimil;i (11'). 

 ( T ) / = ModJ a fh .' 1 [- '^ •- - (-^ + ?/')](!+ -}p)- 



Sinrr ''A .r, üiid ,: nro nil very .-;mn11, ^\c rrin writo 



wliovo c stiiiids for -4- ( -7— + ,,/ Y 



'l\'ikiiiu' ])()l:!r coordiiKites in llio riulif circuLir ^ediDH (.>(' llie 

 (■yliii(l(i- willi the ])n\r on tlio axis, we in:iv writ«' 



d(T = a dx d(f, 



y = a sin c, z -- a {] —cos ç). 



Trdrodnrina' Ihoso expressions in (1), we o-ot Cor 1lie intensily oC Ilic 

 difiV:ieled rny 



( 2 ) Z = Mod.' a fj'dx dif e' ^ ^'' + ""' •''""' *^\ 1 + / 2 rr /> ,- ,r (1 - cos ^')] 



Tn intcgrnting tlie above expression with resper-t to rr, we mnsl (]is- 

 tingnish two eases according as D lies williin or witliout Ilic 

 geometrica I shadow. 



Let 0/1=^5, and A B = h ; tlien the integratimi willi resj^ect 

 to X ninst extend, vvlien D lies within tlie geoinetrical shadow, from 



ß to ß + h. 



When D is onlside tlie geometrical shadow, tlie limits ot" integratioii 

 must he trom 



— ß to h — ß. 



The iritegration with respect t(T tr mnst extend oyer the wliolo 

 lenath oi' the slit. 



