Question

Name the only medium in which the speed of light is equal to that of vacuum.

Answer 1

air is the medium hope it helps you

Answer 2

ACTUALLY there's no medium in which the speed of light is equal to that of vacuum.

THE REFRACTIVE INDEX OF AIR(at normal temperature and pressure) IS 1.00029 W.R.T VACUUM.

Hence, we APPROXIMATE this value to 1.

Hence, we APPROXIMATELY say that the speed of light in air is equal to that of in vacuum.
Hope it helped u...☺️☺️✌️

~SunTheHelpingHand