105 
however. In order to explain this, the wedge-form of the quartz 
plate should be taken into account. 
6. The distance of the lines in the field of the compensator with 
two wedges, placed in opposite direction, having equal angles and 
their principal planes perpendicular to each other, shows that the 
difference of phase in the wedge varies from one rim of the beam to 
the other by a, the width of the incident beam being abont 8 mm. 
The angle of the wedges is 15’. Call this ¢, then for two rays with 
mutual distance 2, the change of the difference in the paths in the 
wedge becomes d,—d,—exr and the change of the phase-differences 
is determined by d,=d,(1l Herv), in which ¢,=e:d,. In this d, 
is the path, that one of the rays passes over in the wedge. Let a be 
ian A. Let «, and A be taken as infinitely small. Let further 
a 1 iy 
the amplitude of the beam of light in the focal plane of the object 
lens behind the wedge be called 1, when the incident beam is 1 mm. 
wide. Then. from the equation in (4) follows, with neglect of quantities 
of the 2nd order: 
A =— Asind, (l + 6,2); B=1— 4A’ sin? d, (1 + ez); 
0—=Aeosd, (l Hee); Z=—tar td, (l + ea). 
From the analyzer issue beams of light with amplitudes 
Acos(w—@)dz and Bsin(w—@)dx.and phases y and 4 Hy. In 
order to obtain the value of the light-vector in the focal plane, these 
amplitudes must be composed, and then we have to integrate 
over the width x of the beam. We can, however, immediately write 
_ down the components of the total amplitude in two directions at 
right angles to each other, viz. 
X= [[A cos op — 6) cos x — B sin ( — 8) om 1] da 
‘0 
r=ftA cos (Wy — 0) sin y + B sin (W — 0) cos X] dz. 
0 
By substitution of the values A, B,y, and 6 indicated here, and 
neglect of quantities of the 2rd order, we get for the intensity of 
the light: 
Lome? a LA, —2 AA, cos d, (1 + 2) |. 
In this: 
