832 



Prof. C. Y. Raman and Mr. G. L. Datta on 



tor cases (1), (J), and (2) are shown diagram matically in 

 fig. 3 (a), (b), and (c) respectively. 



Fig. 3. 



It will be seen from the manner of formation that in the 

 cases (■£) and (-^), the pencil undergoing multiple reflexion 

 deviates from the geometrical path at entry, whereas in (2) 

 and (3) this occurs at emergence. In all the cases, the 



