Question

which term is defined as the ratio of the speed of light in a vacuum to the speed of light in the material it is passing through?

angle of reflection

angle of incidence

index of reflection

index of refraction

Explanation:

The angle of reflection/incidence refers to angles of light rays during reflection, not a speed ratio. The index of reflection is not a standard term. The index of refraction is defined as the ratio of the speed of light in a vacuum ($c$) to the speed of light in a medium ($v$), i.e., $n=\frac{c}{v}$.

Answer:

index of refraction