With what speed would an electromagnetic wave move through a material with an index of refraction of 1.85?

The speed of electromagnetic wave in the material would be 1.162 * 10⁸ m/s

Explanation:

We know that electromagnetic waves travel in a vacuum with the speed of the light i. e. 3*10⁸ m/s

Refractive index or index of refraction refers to the ratio of the speed of light/wave in vacuum to speed of the light/wave in a medium.

RI = speed of wave in vacuum (c) / speed of the wave in medium (v)

RI = c/v

v=c/RI

Substituting the values of RI as 1.85 and speed of wave in vacuum as 3*10⁸ m/s

v (speed of the wave in medium/material) = 3*10⁸ / 1.85 = 1.162 * 10⁸ m/s