The index of refraction for a vacuum is?

Question

A. 1.20

B. 0.00

C. 1.0

D. 0.1

Answer 1

1 by defintion

Even the index of air is slightly higher than 1 and depends on temperature .

Answer 2

The answer if 'C". 1.0...

The index of refraction is the ratio of the speed of light in a vacuum to the speed of light in a medium under consideration. It is also known as the refractive index...

Answer 3

The index of refraction of a medium is a measure for how much the speed of light is reduced inside the medium, as a ratio to a vacuum.  Since a vacuum is 1 times a vacuum, the answer is 1.

  

Answer 4

The vacuum being the reference for most things, you can bet on most of the indexes being 1 by definition (i.e. just because we say so :-)).

Definition: "The index of refraction is a measure of the optical density of a material. Or, you can say it is the ratio of the speed of light in a vacuum to the speed of light in a material."