Question

Does a ray of light incident normally on a refracting surface does not suffer any refraction?

Answer 1

Yes.

According to snell's law

${\mu }_{1}sini={\mu }_{2}sinr$

When rays is perpendicular to surface and incidence angle is $i=0$

So ${\mu }_{1}sin0={\mu }_{2}sinr$

$sinr=0$

$r=0^o$

So ray will pass without deviation.