UV light is effective in destroying bacteria if it is around 300 nanometers. It can produce Vitamin D in the human body if it is around 320nm, but over exposure causes sunburns. The electromagnetic spectrum is a spectrum of all light that we no of. It goes from Billionths of an angstrom to tens of millions of angstroms. And there is still more to explore.
Visible light makes up a very small part of the whole spectrum.
In fact it is only from 3200-7000 angstroms. First on the spectrum are Gamma rays, then x-rays, next is UV light. Then are visible light, infrared and radio waves, respectively. Visible light runs through blue to green to yellow to orange to red. Red light is the least energetic and close to infrared and radio on the spectrum.