Indian Maharashtrian Bridal Jewellery Collection 15

Maharashtrian Bridal Jewellery. 
By Aamir Mannan.
7.REFRACTIVE INDEX AND ITS MEASUREMENT

Thus the ray AO is refracted along OA', apart from the small fraction of light which is reflected at O, as indicated by the dotted line. similarly, the ray BO is refracted along OB', as we 

consider rays which form greater angles with the normal, NOM, we reach an angle where the refracted ray only just grazes along the surface, OQ, between the two media. this angle is know as the critical angle, and all ray reaching O form the denser medium at angle greater than the critical angle are totally reflected back into the denser medium, it being physically impossible for any light form such rays to
penetrate into the rarer medium. in the post, the angle COM can be considered as the critical angle of incidence; all the light s thus totally reflected along OC", and any other rays, such as DO, with a still larger of incidence, is, of course, also totally reflected. it is important to realise that the size of the critical angles will depend upon the relations between the reflactive indices of the denser and the rarer medium.