LEDs And IREDs:

Depending on the accurate mixture of semiconductors used in produce, visible light of any color, and also infrared (IR), can be generated whenever current is passed via a diode in the forward direction. The most general color for a light-emitting diode (LED) is bright red, though LEDs are available in many diverse colors. An infrared-emitting diode (IRED) generates energy at wavelengths a little longer than those of visible red light. These are termed as near-infrared (NIR) rays.

The intensity of energy discharge from an LED or IRED depends to some extent on the forward current. As the current increases, the brightness rises up to a certain point. When the current continues to increase, no further rise in brilliance occurs. The LED or IRED is then said to be in a state of in saturation.