802 Experiments on Polarized Rontgen Radiation. 



Absorption of polarized X-rays by Tourmaline. 



For light in the visible spectrum, tourmaline is a double 

 refracting crystal in which the ordinary ray is absorbed i£ 

 the crystal is thicker than 1 or 2 mm., while the extra- 

 ordinary ray is transmitted without loss of intensity. 



The absorption of a tourmaline crystal cut parallel to the 

 optic axis was determined when : — (1) the optic axis was 

 parallel to the plane of polarization ; (2) the optic axis was 

 perpendicular to the plane of polarization. If X-rays behave 

 in a similar manner to light, the absorption in the two cases 

 should show great dissimilarity. 



The results are shown. 



Absorption by tourmaline crystal cut parallel 

 to optic axis. 



Absorption when axis of Absorption when axis of 



crystal was parallel to crystal was perpendicular 



plane of polarization to plane of polarization 



of X-rays. ' of X-rays. 



549 per cent. 54*1 per cent. 



58-9 „ 59-9 



o8-5 „ 59-1 



57-2 „ 59*8 



58-5 „ 58-5 



These results show that the absorption of a plane-polarized 

 beam of! X-rays by tourmaline crystal cut parallel to the optic 

 axis is independent of the orientation of this axis with 

 reference to the plane of polarization of the X-ray beam. 



Summary. 



The three substances, iron in a magnetized state, quartz, 

 and active sugar solution have been examined to see whether 

 they have any power of rotating the plane of polarization of 

 X-rays. The X-rays themselves are assumed to be essentially 

 similar to light only of exceptionally short wave-length. In 

 all cases a negative result was obtained, indicating the 

 limited range of wave-length over which the usual rotation 

 formula hold. 



Iron has been shown to absorb a polarized beam of X-rays 

 to the same extent whether magnetized or unmagnetized. 

 The absorption of a plane-polarized beam of X-rays by 

 tourmaline cut parallel to the optic axis has also been found 

 independent of the orientation of its axis with reference to 

 the plane of polarization of the X-rays. 



It is with great pleasure that I thank Professor Barkla for 

 suggesting this research, and also for his encouragement 

 during its progress, 



