What is electromagnetic spectrum
It possible of range of frequencies of electromagnetic radiation.

What are the possible ranges in Electromagnetic Radiation
Gamma Ray, X-Ray, Ultraviolet, Visible, Infrared, Microwave, Radio
What are the size range for Electromagnetic Spectrum
The limit of the size range for long wavelengths is the universe and Planck length for the short wavelength.
What is Visible Light
Visible light is the electromagnetic radiation that is visible to the human eye. It’s wavelength range is 400 nm to 700 nm. It is not the absolute limits of human vision but the approximate range within which most people can see.