694: Prof. G. V. Raman and Mr. K. Seshagiri Rao on 



of the direction of the source, and some asymmetiy may be 

 expected in respect o£ this as well. These indications of 

 theory are supported by observation. 



6. Non-Uniform Films : Oblique Incidence. 



It remains finally to explain the phenomena observed 

 in this case. The general nature of the effects noticed in 

 experiment has already been sufficiently indicated in the 

 first paper o£ the series, and is connected with the case 

 discussed in Section 5 in the same way as the contents 

 of Sections 3 and 4 for the case of normal incidence are 

 related to each other. The increase in the number of 

 rings seen on the film on turning it to an oblique position, 

 the blurring of the rings at certain angles varying with the 

 thickness of the film and ihe plane of observation, the changes 

 of the appearance of the film at different angles of diffraction 

 and in different planes, are precisely what we should expect 

 on the basis of the theory worked out in the present paper, 

 in view of the asymmetrical character of the haloes for an 

 obliquely-held uniform film exhibited in fig. 6. To test the 

 matter even further, a few observations have b<>en made of 

 the angles of diffraction for an obliquely-held film at which 

 a dark ring appears on it. The agreement between theory 

 and observation is here again seen to be satisfactory. 



Table IV. 

 Angle of Incidence, 27° 30'. 



Direction of observation in the plane of incidence 

 towards the plate. 



(jx—\ )t. Angle of observation. 



I obs. 7° 42' 23° 18' 46° 0' 



4X 

 7X 



[calc. 8 50 25 40 55 



fobs. 4 30 10 54- 17 40 28° 10' 4?,° 0' 

 jcalc. 4 10 li 10 20 30 20 46 



Direction of observation in the plane of incidence 

 away from the plate. 



(fi — l)t. Angle of observation. 



4,\ 



obs. 10° 30' 27° (V 

 ealc. 10 9 31 10 



GX 



{e 



obs. 7 24 17 10 31° 0' 



calc. 7 15 15 50 30 15 



