> I don't think we currently know of any practical way to change the wavelength and frequency of electromagnetic waves (within the same medium), and even if th

> I don't think we currently know of any practical way to change the wavelength and frequency of electromagnetic waves (within the same medium), and even if there was, it would likely take so much energy that it would never be efficient to spend the energy this way. Isn't this the entire principle behind using quantum dots in displays? i.e. The quantum dots absorb light from the backlight and then re-emit it as a very specific color band.