When light goes from a vacuum to some medium, like water, its speed and wavelength change, but its frequency \(f\) remains the same. (We can think of light as a forced oscillation that must have the f...When light goes from a vacuum to some medium, like water, its speed and wavelength change, but its frequency \(f\) remains the same. (We can think of light as a forced oscillation that must have the frequency of the original source.) The speed of light in a medium is \(v = c/n\), where \(n\) is its index of refraction.
