The speed of light in two media  $\mathrm{I}\mathrm{and}\mathrm{II}$   are  $2.2\times {10}^8 \mathrm{m}/\mathrm{s}$ and  $2.4\times {10}^8\mathrm{m}/\mathrm{s}$   respectively. The critical angle for light refracting form  $\mathrm{I}\text{\hspace{0.17em}\hspace{0.17em}to\hspace{0.17em}}\mathrm{II}$ medium will be