A student traces the path of a ray of light through a rectangular glass slab for angles of incidence 40degree, 50degree, 60degreeseparately. He observed that the perpendicular distance ‘d’ between the incident ray and emergent ray : (a) increases with increase in angle of incidence. (b) decreases with increase in angle of incidence. (c) remaines the same for all the three angles. (d) first increases and then decreases.