It is more specific to calculating the frequency and wavelength of the speed of light but all the concepts behind it are the same. This very small wavelength is about 120th of the diameter of a hydrogen atom. C30 x 10 8 ms the speed of light in a vacuum This constant c is how fast electromagnetic radiation light for all extensive purposes travels.
The other is h which called Plancks constant.
The variable c is the speed of light. In particular the value for the speed of light in a vacuum is now defined as exactly 299792458 metres per second. The difference in the two frequencies is fed into a modified form of the above equation and a speed is calculated. Therefore light does not only travel at the speed of electromagnetic waves it is an electromagnetic wave.