The index of refraction of a medium is given by:
[tex]\begin{gathered} n=\frac{c}{v} \\ \text{ where } \\ c\text{ is the speed of light in vacuum and } \\ v\text{ is the speed of light in the medium } \end{gathered}[/tex]Plugging the value given we have:
[tex]\begin{gathered} n=\frac{3\times10^8}{1.74\times10^8} \\ n=1.724137961 \end{gathered}[/tex]Therefore, the index of refraction is 1.724137931
