Electromagnetic Wave Spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object has a different meaning, and is instead the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object.
Reference
Wikipedia [Electromagnetic Spectrum]
Visible Light Spectrum
Visible light waves are the only electromagnetic waves we can see. We see these waves as the colors of the rainbow. Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light. Also, EMF stands for Electromagnetic Field.
12 D Ray
Awareness of our Human Energy Field and Spectrum of Frequency supports the beginning of understanding that all and everything around and within us is an Electromagnetic Wave Form and Vibratory Quality. In our Ascension model we recognize and work with 15 Wave Spectrum of Frequency that correlate directly with the Universal Rays (See the Universal Time Matrix) and our individual Chakra systems.
As an example, the 12D Ray is a White Ray (a ray is a term for an electromagnetic wave spectrum) is the consciousness unit and a level of our being, the Avator Christos that manifests on the 12th dimension in the Universal Time Matrix.