A transparent solid cylinderical rod has a refractive index of `2sqrt(3)`. It is surrounded by air. A light ray is incident at the mid-point of one end of the rod as shown in the figure. The incident angle `theta` for which the light ray grazes along the wall of the rod is
A. `sin^(-1)((1)/(2))`
B. `sin^(-1)((sqrt(3))/(2))`
C. `sin^(-1)((2)/(sqrt(3)))`
D. `sin^(-1)((1)/(sqrt(3)))`
