Question

If the speed of light in air is 3.00 · 108 m/s (approximately equal to that in a vacuum) and the speed of light in water is 2.25 · 108 m/s, what is the index of refraction of water?

Answer 1

Answer: 1.333

Explanation:

Index of refraction= n=c/v

Where c is the speed of light in vacuum and v is the speed of light in material ( water) in this case.

n = 3.00.108/2.25.108

n =3.00/2.25

n = 1.333

Approximately 1.33

There is no unit because m/s cancels out m/s

Answer 2

N= velocity in vacuum/velocity in water 
n=3.00*10⁸m/s/2.25 *10⁸m/s= 3.00/2.25 ≈ 1.33

n ≈ 1.33