Infrared, or IR, radiation is a type of electromagnetic radiation that lies between visible light and microwaves. It is invisible to the human eye, but can be felt as heat. IR is emitted by all objects above absolute zero, and the higher the temperature of an object, the more IR it emits.

Some facts about infrared radiation include:

- Infrared radiation was discovered in 1800 by Sir William Herschel, an English astronomer.

- Infrared radiation is used in a variety of applications, including thermal imaging, night vision, remote sensing, and spectroscopy.

- The human body emits infrared radiation, and this radiation can be used to measure body temperature.

- Infrared radiation is used in thermal imaging cameras to create images of objects based on their temperature differences.

- Night vision devices use infrared radiation to allow people to see in the dark.

- Remote sensing uses infrared radiation to collect information about objects from a distance, such as their temperature, composition, and motion.

- Spectroscopy uses infrared radiation to identify the chemical composition of objects.

- Infrared radiation is used in a variety of medical applications, including laser surgery, skin rejuvenation, and pain relief.

- Infrared radiation is used in industrial applications, such as heating, drying, and welding.

- Infrared radiation is used in military applications, such as missile guidance and target tracking.