The index of refraction of a transparent substance is 1.7, and the speed of light in air is 3.00 · 108 s. Calculate the speed of light in the transparent substance.

Given the index of refraction, n and speed of light in the vacuum, c, we can solve for the speed of light in the transparent substance by the equation below.

n = c / v

where v is our unknown.

Substituting the known values,

1.7 = (3 x 10^8 m/s) / v

The value of v is equal to 1.76 x 10^8 m/s.