10 



H. NAGAOKA. 



Unis, B is always greater than -y 2 --* \- ^- -^- , ov b>A; 



hence the coefficient of £' 2 is always negative. The curves of equal 

 intensity ôl near the point of intersection of dark bands are, there- 

 fore two hyperbolae, one of which is conjugate to the other. The 

 lengths of the principal semi-axes a, b, are given by 



The angle # made by £' axis with ? axis is given by 



cos 2 # = 





which evidently is the angle made by a line bisecting the angle between 

 the tangents to <p and ^ at the point of intersection of the bands. 

 We can also prove that the asymptotes coincide with the tangents 

 to (p and y>. 



From the above result, the curve of equal intensity ol near the 

 point of intersection can be easily drawn. These curves will be of 

 great help in studying the actual diffraction figures from those given 

 by theory. 



I here give two examples of these curves, one for a rectangular 

 aperture, and the other for two circular holes of equal size. 



Rectangular aperture. — The expression for the intensity is 



/ sin, a x \- / sm p y V 

 \ ax J \ ßy ) 



where c, «, $ are constants. 



