11)
Thus, the velocity of light depends on electric and magnetic properties of
the medium We shall see in the next chapter that the refractive index of
one medium with respect to the other is equal to the ratio of velocities of
light in the two media The velocity of electromagnetic waves in free space or vacuum is an
important fundamental constant It has been shown by experiments on
electromagnetic waves of different wavelengths that this velocity is the
same (independent of wavelength) to within a few metres per second, out
of a value of 3×108 m/s