speed of light in vacuum and air
Answers
The speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second), and in theory nothing can travel faster than light. In miles per hour, light speed is, well, a lot: about 670,616,629 mph. If you could travel at the speed of light, you could go around the Earth 7.5 times in one second.Light, in a vacuum, travels at 186,283 mps.
Light in air travels 186,200 mps or about 56 mps slower.
Light in another medium like water travels at 139,712 mps. or about 3/4 of light speed in a vacuum.
One must remember that when the photon is traveling in a medium like air or water it is slamming into air or water molecules, being absorbed and re-emitted, absorbed and re-emitted on and on. This absorption and re-emittition changes with the density of the medium slowing it down. The same with glass, clear plastic etc…