On entering into the glass medium light ray bends towards the normal that is light ray gets refracted on entering the glass medium. After getting refracted this ray now travels through the glass slab and comes out of the glass slab by refraction from the other interface boundary. Since ray goes from glass medium to air it again gets refracted and bends away from normal. The incident ray and the emergent ray are parallel to each other.
i is the angle of incidence, r is the angle of refraction and e is the angle of emergence. Angle of incidence and angle of emergence are equal as emergent ray and incident ray are parallel to each other. When a light ray is incident normally to the interface of two media then there is no bending of light ray and it goes straight through the medium.