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BELL SYSTEM TECHNICAL JOURNAL 



where 

 and 



tan 02 = — 



A^2 



sin 6 



sin U = 



cos sin~^ N3 



(3.29) 

 (3.29') 



BEVEL- 



Fig. 3.21 — Position 3 for a plate of general orientation 



With the plate rotated 90° again (180° from position 1), so that the entering 

 beam is in the position shown in Fig. 3.21, the components of the unit 

 vector X3 along the incident beam are 







sings 

 -cosga 



so that 

 or 



where 

 and 



sin 6 = N2 sin gz — N3 cos ^3 



^3 



tan 83 = 



sm y = 



d' + 8z 



N2 

 sin 6 



cos sin~^ Ni 



f / 



03 — 01 



(3.30) 



(3.31) 

 (3.32) 



(3.260 

 (3.33) 



Finally, with the X-ray beam entering as shown by the unit vector X4 

 in Fig. 3.22 (270° from position 1) the components of ^i are 



COSgi 



sing4 

 



so that 

 or 



sind = N2 sin gi + Ni cos 



(3.34) 

 (3.35) 



