What is the speed of light?
Such a physical phenomenon as light is understandable to everyone, and does not require additional descriptions. Where the human eye is able to discern objects and outline their outlines, there is light. It is worth only mentioning that light in its physical nature is formed by electromagnetic waves propagating with a certain frequency from 790 to 385 terahertz.
Characteristic speed of light
At the same time, the light has such an interesting property as the speed with which it reaches the object illuminated by it. What is the speed of light, scientists have long figured out for themselves, and provided us with accurate data. The standard of the speed of light propagation is a constant value, which is measured in the absence of air, vacuum, and is equal to approximately 300 000 km / s, and if to be more scrupulous - then 299 792 458 m / s. This constant is denoted by the Latin letter C, and, belongs to the category of fundamental.
But, in terrestrial nature, such conditions are possible, only by artificial means.Therefore, what is the speed of light in the natural conditions of the Earth, a problem calculated by a special formula that takes into account the refractive indices of the medium and the properties of light scattering. It is also worth distinguishing the phase and group velocity of light. But one thing remains constantly true: these speeds, practically, always remain lower in value of a constant value of C.
- The year in which accurately determined the speed of light, using the reference meter: 1975.
- The magnitude of the speed of light is used in Einstein's theory of relativity.
- The light beam for 2.5 seconds can overcome the path from the Earth to the Moon there and back.
- Travel time of outgoing light from the Sun to our planet is 8 minutes 18 seconds.