Question

"during refraction of light through the glass slab incident ray and emergent ray are parallel to each other" Explain

Answer 1

$your \: answer$
now for this consider a glass slab now a light is incident on it and it strikes the glass surface now as the light is travelling from rarer (air) to denser medium (glass) it will bend towards the normal following the principle of refraction

2) now when the light has refracted it again refracts from (glass) denser medium to (air) rarer medium and will now bend away from normal

therefore the result we will get is that emergent Ray is parallel to incident ray

hope helps