Visible light is part of the electromagnetic spectrum extending from 700 nm wavelength, up to 400 nm wavelength, in other words visible light is a part of the electromagnetic wave that is generated and has all wavelengths.
There are many attempts to measure the speed of light throughout history. It is logical and logical to think of the law of speed, which states that it is equal to distance divided by time, but with light, it is not that simple, it is very fast, Which is equal to (299,792,458 m / s).