The speed of light in a certain substance is 83% of its value in water. what is the index of refraction of this substance?

The Index of Refraction formula is:

n = c / v,

where c is the speed of light in vacuum and v is the speed of light in that substance.

For water: n (water) = 1.33

1.33 = c / v (water)

v (water) = c/1.33

For a certain substance:

n = c : (0.83 * c/1.33) = 1.33 / 0.83

n = 1.6

Answer: The Index of Refraction of this substance is 1.6.