340 



H. NAGAOKA; DIFFRACTION PHENOMENA 



TP J? 



The following table gives the values ôf -^7- + K and -p — K. 



The formulae given above apply only to points far from the edge 

 of the circular image. The most interesting case connected with the 

 present problem is the investigation of the intensity at points in the 

 very neighbourhood of the geometrical rim, where under certain 

 circumstances the well-known phenomenon of drop-formation makes its 

 appearance. As the semi-convergent expression for Jô 2 (f>) + Ji(f>) is no 

 longer available in the neighbourhood of the rim, we shall have recourse 

 to another method of integration for that portion of the region, where 

 Jo% ) + Ji(., ) must be expanded according to ascending powers of p. 



For this purpose, we shall divide the region of integration into 

 two parts by describing a circle with radius x 1 about the point where 

 the intensity is sought ; at points of the periphery not included within 

 the circle thus described, we can use the semi-convergent expression 

 and apply the method of integration given above, while in the interior 

 we have to proceed in the following manner. 



As the point lies very near the periphery, o is a very small quan- 

 tity and h is very near unity ; whence, if p be expressed in terms of 



