Since school time we know that speedlight, according to the laws of Einstein, is an insuperable maximum in the Universe. The distance from the Sun to the Earth, the light travels in 8 minutes, which is approximately 150,000,000 km. Neptune reaches only 6 hours later, but spacecraft takes decades to overcome such distances. But not everyone knows that the value of speed can vary considerably depending on the environment in which the light passes.
Light speed formula
Knowing the speed of light in vacuum (c ≈ 3 * 108 ms), you can define it in other environments, based onof their refractive index n. The very formula of the speed of light resembles the laws of mechanics from physics, or rather, the determination of distance using the time and speed of an object.
For example, we take the glass, the coefficientrefraction which is 1.5. According to the formula for the speed of light v = c n, we obtain that the speed in this medium is approximately 200,000 km / s. If you take a liquid, such as water, then the speed of propagation of photons (particles of light) in it is 226,000 km / s with a refractive index of 1.33.
Formula of the speed of light in the air
Air is also a medium.Therefore, it has a so-called optical density. If in vacuum photons do not encounter obstacles on their way, then in the medium they spend some time on the excitation of atomic particles. The denser the environment, the more time is spent on this very excitement. The refractive index (n) in air is 1,000292. And this is not much away from the limit of 299 792 458 m / s.
American scientists managed to slow downlight to almost zero. More than 1/299 792 458 sec. light speed can not overcome. The fact is that light is the same electromagnetic wave as x-rays, radio waves or heat. The difference is only in the difference between the wavelength and frequency.
Интересным фактом считается отсутствие массы у photon, and this indicates the absence of time for a given particle. Simply put, for a photon that was born several million, or even billions of years ago, not a second passed.
