﻿Relation between X-ray Wave-lengths and Absorption. 407 



The measurements show clearly in many cases that through 

 over-exposure of the plate errors may be produced in the 

 results, since on increasing the time of exposure, and con- 

 sequently increasing the precipitate of silver on the plate, an 

 apparent alteration can be found in the wave-length of lines 

 which are unsymmetrically broadened. 



The present research has been carried out at the Physical 

 Institute of the University of Vienna. I take this opportunity 

 of expressing my best thanks to Hof rat Professor Exner and 

 Professor Haschek, at whose suggestion the work was under- 

 taken, for their active interest and helpful criticism during 

 its progress. 



May 23, 1914. 



XLIII. The Relation between certain X-ray Wave-lengths and 

 their Absorption Coefficients. By W. H. Bragg, D.Sc, 

 R.R.S., Cavendish Professor of Physics in the University 

 of Leeds * 



IN the figure is shown the X-ray spectrum of rhodium, 

 in the second order, given by the (111) planes of 

 calcite. The abscissae denote the glancing angle, that is 

 to say the angle between the incident X ray and the crystal 



Fia 1. 



v 



& 



Secona 



/>7 Ca/c//-<? 

 ' orc/er. 



{///) 







w 



2& 



W 



/a//ac//'um 

 7b/rt> 



orWer. 



25 



{///) 



40' 



Si/y 



*~ 



KS 



(//crrrwrrc/////) 

 /y'rsf or o'er 



S//rer 



//r c//a/?ro/7rf 



r///> 





T6//-C/ 



arc/er* 







. 





t 





*o' 7 20 50' 24" 20' 40' 



planes. The ordinates represent the readings of the electro- 

 scope attached to the X-ray spectrometer. In determining 

 this spectrum, readings were taken every two minutes of 

 arc, and every minute in the important regions. Each dot 

 in the figure represents a separate measurement, but only 

 * Communicated by the Author. 



