Since the ray strikes the glass slab at an angle of 90°. Therefore
Angle of incidence = 00.
Thus the ray of light will pass straight without any deviation as shown in the figure below.
Laws of Refraction of light;
µ = \(\frac{Sin\,i}{Sin\,r}\)
Refractive index=1.5
Thus angle of refraction is given by
1.5 = \(\frac{0}{Sin\,r}\)
On solving, we get
sin r = 0
Thus the angle of refraction is 0°
Thus the refracted ray is perpendicular to the surface of the glass slab as shown in the above diagram.