The speed of light in media $M_1$ and $M_2$ is $1.5 \times 10^8\,\text{m/s}$ and $2.0 \times 10^8\,\text{m/s}$ respectively. A ray of light enters from medium $M_1$ to $M_2$ at an incidence angle $i$. If the ray suffers total internal reflection, the value of $i$ is