if light travels through plastic at the speed of 2.2x10 over 8 m/s. what is the index of refraction

Answer 1

Did you mean 2.2 * 10⁸ ?

The index of refraction, n, is defined as the ratio of the speed of light in a medium to the speed in a vacuum, The latter, typically called "c" is 3.0 * 10⁸

So, n = 2.2 / 3