what mediums are used to understand the idea of it?
In a medium, light usually does not propagate at a speed equal to "c"; further, different types of light wave will travel at different speeds.
Speed of light
In a medium, light usually does not propagate at a speed equal to "c"; further, different types of light wave will travel at different speeds. 
who discovered the speed of light in a vacuum Witelo what is the numerical value of it? As a dimensional physical constant, the numerical value is different for different unit systems. how important is it in the field of physics? It is independent both of the motion of the wave source and of the inertial frame of reference of the observer. were there any experiments conducted to discover something faster than light? Yes, but they do not travel fast than light who did such experiments? UNANSWERABLE what is its part in spaceflights? There is a brief delay from the source to the receiver, which becomes more noticeable as distances increase; was significant for communications between ground control and Apollo 8 what is the special relativity in relation to it? The speed of light in vacuum "c" featured as a fundamental constant, also appearing in contexts unrelated to light.
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Speed of light [SEP] In a medium
In a medium, light usually does not propagate at a speed equal to "c"; further, different types of light wave will travel at different speeds. The speed at which the individual crests and troughs of a plane wave (a wave filling the whole space, with only one frequency) propagate is called the phase velocity "v". A physical signal with a finite extent (a pulse of light) travels at a different speed. The largest part of the pulse travels at the group velocity "v", and its earliest part travels at the front velocity "v". The phase velocity is important in determining how a light wave travels through a material or from one material to another.