Relationship between the propagation speed, frequency, and wavelength
v = f \lambda
(a) The speed of light in vacuum
According to Einstein's theory of relativity, light speed in vacuum is an absolute constant. It does not depend on any of the above factors or any other factor
b) The speed of light in medium (glass or water)
(i) The speed of light in medium does not depend on the source's nature.
(ii) The direction of propagation does not influence the wave propagation speed.
(iii) The speed of light in medium does not depend on the motion of the source in relative to the medium, however depends on
the motion of the observer with respect to the medium.
(iv) It depends on the wavelength of light,
v = f \lambda
v \propto \lambda
(v) It does not depend upon intensity of light