Light is a form of electromagnetic radiation that exists across a spectrum of wavelengths and frequencies. The visible spectrum is the portion of this spectrum that can be detected by the human eye, ranging from about 400 to 700 nanometres Light Spectrum(nm) in wavelength. However, light also exists outside of the visible spectrum, in both the ultraviolet (UV) and infrared (IR) regions.

The UV region includes wavelengths shorter than 400 nm and frequencies higher than those of visible light. It is divided into three sub-regions: UV-C (100 to 280 nm), UV-B (280 to 315 nm), and UV-A (315 to 400 nm). UV-C has the shortest wavelengths and highest frequencies and is the most damaging to living organisms, while UV-A has longer wavelengths and lower frequencies and is less harmful.

The IR region includes wavelengths longer than 700 nm and frequencies lower than those of visible light. It is divided into three sub-regions: near-infrared (NIR, 700 to 1400 nm), mid-infrared (MIR, 1400 to 3000 nm), and far-infrared (FIR, 3000 to 1 mm). NIR is used in applications such as remote sensing, fiber optic communication, and medical imaging, while MIR is used in spectroscopy and chemical analysis. FIR is used in applications such as thermal imaging and sensing.

In addition to the visible, UV, and IR regions, light also exists in other regions of the electromagnetic spectrum, including radio waves, microwaves, X-rays, and gamma rays. Each of these regions has unique properties and applications.

Overall, the categorization of light into different regions of the electromagnetic spectrum is based on its wavelength and frequency, and each region has unique properties and applications.