CBSE Class 10 Answered

When light passes through glass, it encounter two surfaces, one is the
entry side and the other exit side. A light ray is refracted(bent) when
it passes from one medium to another, thereby changing its speed.If the
two interface surfaces are parallel to each other, all of the bending (
or dispersion)that takes place at the first interface is exactly
reversed or counter effected at the other end, undoing the effect of
first interface.

But, still the emerging ray is slightly displaced from the incoming
ray, travels in the same direction as the incoming ray and all
wave-lengths that got separated at the first interface now recombined.