$\left(\mu_{ r }=1\right)$
\(\Rightarrow \sin i>\sin \theta_{C}\)
\(\Rightarrow \sin i>\frac{\mu_{R}}{\mu_{D}}\)............\((1)\)
Also \(\mu=\sqrt{\mu_{ r } \epsilon_{ T }}\)
\(\frac{\mu_{ R }}{\mu_{ D }}=\frac{\sqrt{1 \times 1}}{\sqrt{4 \times 1}}=\frac{1}{2}\)
From (1), \(\sin i>\frac{1}{2} \Rightarrow i>30^{\circ}, i =60^{\circ}\)