Electromagnetic radiation is a form of energy, the light being a part of it. The electromagnetic spectrum is divided into regions which are classified by their wavelength ranges. The classification is somewhat arbitrary and it is rather determined by instrumentation than any other objective reason. The atomic spectrometry deals with absorption and emission of radiation from the visible and ultraviolet domains of the spectrum.
The behaviour of light can be extrapolated to the whole electromagnetic spectrum. In atomic spectroscopy the corpuscular theory offers explanation for the processes involved. You may ask me: "Then, why is the energy of radiation presented in terms of wavelength ?". If there was no confusion it would have been to easy to understand and learn.
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