A transparent block A having refractive index μ=1.25 is surrounded by another medium of refractive index μ=1.0 as shown in figure. A light ray is…

A transparent block A having refractive index $\displaystyle \mu=1.25$ is surrounded by another medium of refractive index $\displaystyle \mu=1.0$ as shown in figure. A light ray is incident on the flat face of the block with incident angle $\displaystyle \theta$ as shown in figure. What is the maximum value of $\displaystyle \theta$ for which light suffers total internal reflection at the top surface of the block ?