A glass slab has thickness ' $t^{\prime}$ and refractive index $\mu$. If a ray of light from air is incident on a glass slab, at an angle of incidence equal to the angle of total internal refraction of glass, then the displacement of the ray due to this slab in terms of thickness and refractive index of glass $\mu$ is:
(a) $\frac{t}{\mu}\left[1-\frac{1}{\sqrt{\mu^{2}-1}}\right]$
(b) $\frac{t}{\mu}\left[1+\frac{1}{\sqrt{\mu^{2}+1}}\right]$
(c) $\frac{t}{\mu}\left[1-\frac{1}{\sqrt{\mu^{2}+1}}\right]$
(d) $\frac{t}{\mu}\left[1+\frac{1}{\sqrt{\mu^{2}-1}}\right]$