a ray of light which strikes a glass slab from air at normal incidence passes through the slab

Answer Details

When a ray of light travels from air into a denser medium, such as a glass slab, it slows down and changes direction, which is called refraction. However, when the incident ray is perpendicular to the surface of the glass slab, it is called normal incidence, and the ray does not change direction, but only changes speed as it passes through the glass. Therefore, the answer is that the ray of light will be undeviated and undisplaced at a lower speed. So, the correct option is undeviated and undisplaced at a lower speed.