According to Snell's law (sin i/sin r)= r.index. Justify Snell's law for i=0, where i ind r are angle of incidence and angle of refraction respectively.

then refraction index = 0 and the ray passes without refracting , but i m not sure of the crrct reason / explanation to give , u can search ofn google , till then i will ask my teacher morev on this ,  when he taught me snells law and we applied it in a prism q , he told that if the ray coincides with the mnormal it passes without deflecting , hope it helps you

 

regards ,

Krutarth 

 

thank you and have a nice day and do let me know if u have any other q ..