Question

multiple choice question
which term describes the measure of how much a substance slows the velocity of light?

refractive index
resolution
focal length
total magnification

Explanation:

Refractive index is defined as the ratio of the speed of light in a vacuum to its speed in a given substance, directly measuring how much the substance slows light. Resolution refers to clarity of detail, focal length relates to lens optics and light focusing, and total magnification is about enlarging an object's apparent size, none of which describe light slowing in a substance.

Answer:

A. Refractive index