Ii^tt<rm«!tm of "§nUxUxnm" in iht 



Translated from the German Treatise of Messrs. 



N^GELI AND ScHWENDENER, '^'^ DaS MiCROSKOP;,'' 



By H. E. FRIPP. 



THE phenomena of diffraction shew that Hght suffers a charac- 

 teristic change in passing through objects whose structure 

 contains very minute particles. In general terms this change 

 may be described as the breaking up of a parallel beam of light 

 into a group of rays diverging 

 with wide-spread angle, and 

 exhibiting a regular series of 

 maxima and minima of inten- 

 sity of light due to difference 

 of phase of vibration. 



Let A£ (fig. i) represent 

 an object having alternate 

 transparent a h and non- 

 transparent parts, Aa IB; 

 and let c represent a parallel beam incident upon the 



