Answer:
Refractive index of a glass is 1.5 means that the speed of light travels 1.5 times SLOWER in that glass than in a vacuum.
Explanation:
Refractive index is defined as a ratio between the speed of light in a vacuum and the speed of light in a medium. Since the refractive index is a ratio between two speeds it is a dimensionless number. For the glass, having a refractive index of 1.5, means that the speed of light travels 1.5 times SLOWER in that glass than in a vacuum.
