If a seventh methyl group is added, the resulting dye is Methyl green. The colour of the dye is caused by the absorbance of electromagnetic radiation. We have constantly referred to the wavelength that is absorbed , in the singular, but a simple scan of a dye solution with a spectrophotometer shows that dyes do not remove a single wavelength. Plotting the wavelength absorbed against the degree of absorbance usually results in a display resembling a bell curve. If any part of this curve is in the visible range, the dye will appear coloured.
White light is a mixture of wavelengths.
By the process of resonance, previously described, the electron cloud will respond to the energy contained in that radiation by absorbing it, and removing it from the spectrum. As a consequence the white light will cease to be white and will display the colours of the wavelengths left over. The transmitted light will have the complementary colour to the wavelengths removed. The Effect When light illuminates a dye, some of it is absorbed as energy. Since energy is not destroyed, something must then happen.