Question

please please please solve this question ........

Answer 1

n=c/v
v = (3*10^8) /1.7
That will be the answer

Answer 2

here we will use snell's law that is given by V1/V2=n2/n1
here the refractive index in vaccum is 1 thus
3*10^8/v=1.7/1
1.76*10^8m/s