16 



Mr. T. K. Chinmayam on the Flow of 



towards or away from the objective, the phenomena at 

 different planes y^=-d could be observed. 



The photometric arrangement nsed to study the relative 

 intensity of the fringes was based upon a polarization method. 

 The beam o£ light was plane-polarized by passage through a 

 nicol before falling on the cylinder. The eyepiece (a low- 

 power one) was moved off to a pretty large distance behind 

 the objective, and two narrow slits cut out of aluminium-foil 

 and pasted on two glass strips were mounted, one above the 

 other, between the eyepiece and the objective, so as to 

 allow a small relative motion which could be controlled by a 

 micrometer-screw. A thin mica plate was also fixed up on 

 the upper one, which was movable in the experiment, the 

 thickness of the plate and its orientation with respect to 

 the slit being adjusted by trial so that under the conditions 

 of the experiment it circularly polarized the light falling on 

 it. The field was viewed through another nicol fitted with a 

 graduated circle and mounted just behind the slits. The 

 lower slit was always set on the first bright band, while 

 the upper one was set successively on the different maxima 

 and minima. Equality of illumination was obtained in each 

 case by rotating the analysing nicol. The reading for the 

 crossed position of the analyser being also taken, the ratio 

 of the intensities of illumination could be easily calculated. 

 Thus if y\r be the orientation of the analyser in any case 

 (i/r being reckoned from the crossed position) and I, I 

 the intensities of illumination of the upper and lower slits 

 respectively, 



I/I =sin 2 ^. 



Readings were taken for the first few bands on the planes 

 z/ = and y — 0'5 cm., and are given in Table I. with the 

 corresponding values calculated from theory. 









Table I. 









yio- 



y=0. 



y=0*5 cm. 



Maxima. 



Minima. 



Maxima. 



Minima. 



Obsd. 



Calcd. 



Obsd. 



Calcd. 



Obsd. 



Calcd. 



Obsd. 



Calcd. 



i 



1-00 



1-00 



0-09 



0-07 



1-00 



1-00 



0-46 



0-42 



2 



0-96 



TOO 



0-08 



0-07 



0-91 



0-93 



0-45 



0-44 



3 



1-00 



1-00 



0-12 



0-07 



0-91 



0-91 



0-52 



0-46 



4 



0-94 



1-00 0-15 



0-07 



0-83 



0-90 



0-52 



0-46 



