A long rectangular slab of transparent medium of thickness d placed on a table with its length parallel to the x-axis and width parallel to the axis. A ray of light travelling inair makes a near normal incidence on the slab as shown. Taking the point of incidence as orign (0,0,0). The refraction index `mu` of the medium varies as `mu=(mu_(0))/(1-(x/r)` where `mu_(1)` and `r(gtd)` are constants. The refractive index of air is `mu_(0)`

The x-coordinate of the point A where the ray intersects the upper surface of the slab air boundary is

Options

A. the ray retraces its path
B. the ray travels along the positive x-axis
C. the ray will travel parallel to y-axis
D. The ray will make certain angle `theta(gt30^(@))` with positive y-axis and pass along the line

Answer

C