The index of refraction for a medium is:

W) the ratio of the angles of refraction of red light and blue light in the medium

X) the angle of refraction for monochromatic light in the medium

Y) the ratio of the speed of light in the medium to the speed of light in a vacuum

Z) the ratio of the speed of light in a vacuum to the speed of light in the medium
Z) THE RATIO OF THE SPEED OF LIGHT IN A VACUUM TO THE SPEED OF LIGHT IN THE MEDIUM