Question

The speed of light in benzene is 2.00×108 m/s. what is the index of refraction of benzene?

Answer 1

The index of refraction of a material is the ratio between the speed of light in vacuum, c, and the speed of light in that material, v:
$n= \frac{c}{v}$
where the speed of light in vacuum is $c=3 \cdot 10^8 m/s$. The speed of light in benzene is $v=2.00 \cdot 10^8 m/s$, so we can use the previous relationship to find the refractive index of benzene:
$n= \frac{3 \cdot 10^8 m/s}{2.00 \cdot 10^8 m/s}=1.5$