જો \( i   > \theta_c\) અથવા  \(sin\,\, i > sin\,\, \theta_c\)

\(\sin \,\,i\,\,\, > \,\,\,\frac{1}{\mu }\,\,\,\left[ {as\,\,\,\sin {\theta _c} = \,\,\frac{1}{\mu }} \right]\,\,\,\,......\,\,\,(i)\)

O પાસે સ્નેલના નિયમ પરથી  \(1 × sin \theta  = \mu \,\, sin r \)

\(\Delta \,\, OPR\) માં ,\( r + 90 + i = 180\)   \(  r + i = 90°\)

તેથી  \(\,sin\,\theta \,\, = \,\,\mu \,\,sin\,\,(90 - i)\,\,  = \,\,\mu \,\,cos \,\,i\,\,\,\, \Rightarrow \,\, cos \,i\,\,\, = \, \frac{{sin\theta }}{\mu }\)

તેથી  \(sin\,i\,\, = \,\,\,\sqrt {1 - co{s^2}i} \,\,\, = \,\,\,\sqrt {1 - {{\left[ {\frac{{\sin \theta }}{\mu }} \right]}^2}} \,\,\,......\,\,\,(ii)\)

તેથી \(sin\,\, i\) નું મૂલ્ય સમીકરણ \((ii)\) માંથી \( (i)\) માં મૂકતાં,

\(\sqrt {1 - \frac{{{{\sin }^2}\theta }}{{{\mu ^2}}}} \,\,\, > \,\,\frac{1}{\mu }\,\,\,i.e.,\,\,\,{\mu ^2} > \,\,\,1\,\, + \,\,{\sin ^2}\theta \,\,\,\therefore \,\,\,\,{\mu ^2} > 2\,\,\,\,\,\,\)

                                                            \(\because \,\,\,{({\sin ^2}\theta )_{\max }} = \,\,\,1\,\,\)

\(\, \Rightarrow \,\,\mu \,\, > \,\,\,\sqrt 2 \,\,\,\,\,\therefore \,\,{\mu _{\min }} = \,\,\sqrt 2 \)