Cod liver oil - a potentially toxic source of Vitamin A: Hypervitaminosis A can result from ingestion of too much vitamin A from diet, supplements, or prescription medications.
This visible light region consists of a spectrum of wavelengths that range from approximately 700 nanometers (abbreviated nm) to approximately 400 nm. Expressed in more familiar units, the range of wavelengths extends from 7 x 10 -7 meter to 4 x 10 -7 meter.
Gamma rays, visible light, and radio waves are all examples of electromagnetic radiation, and you're right that radio waves are on one end of the spectrum (with a wavelength of meters), gamma rays are on the other end (with a wavelength of about 10-12 meters) and visible light is somewhere in between (with a wavelength of around 5 x 10-7 meters).