Why does a light ray incident on a rectangular glass slab immersed in any medium emerge parallel to itself? Explain.

(N/A) When a light ray enters a rectangular glass slab,it undergoes refraction at two parallel interfaces.
$1$. At the first interface (air-glass),the light ray bends towards the normal because it travels from a rarer to a denser medium.
$2$. At the second interface (glass-air),the light ray bends away from the normal as it travels from a denser to a rarer medium.
$3$. According to Snell's Law,the angle of incidence at the first surface is equal to the angle of emergence at the second surface because the opposite sides of the rectangular slab are parallel.
$4$. Consequently,the emergent ray is parallel to the incident ray,but it undergoes a lateral displacement.