Infrared (IR)
The longest visible red wavelength is ~750nm, and beyond this is the infrared (IR) spectrum. Near-infrared (N-IR) continues form the visible up to the mid-infrared (mid-IR) at about 2000nm, with the far infrared (far-IR) beyond this to ~1mm.
Related Terms: Light, Mid Infrared, Near Infrared, Ultra-Violet (UV), Visible Spectrum (VIS)