Infrared Radiation

Referring to NCERT Class 12, Chapter 8 (Electromagnetic Waves), infrared radiation lies just beyond the red end of the visible spectrum, with wavelengths from about 700 nm to 1 mm. All objects above absolute zero emit infrared, and warmer bodies emit more intensely, which is why it is commonly termed heat radiation. Satellites exploit this by sensing infrared emission to determine the temperature of clouds and land surfaces even in darkness, since detection does not need reflected sunlight. Ultraviolet rays have shorter wavelengths than visible light and are associated with high-energy processes, not thermal emission from warm bodies. Gamma rays originate from nuclear transitions and carry enormous energy, unrelated to ambient heat sensing. Microwaves are used in communication and radar and, while thermal in some contexts, are not the primary heat radiation emitted by moderately warm surfaces. A plausibility check based on the blackbody peak of everyday-temperature objects, which falls in the infrared band, confirms that infrared radiation is the correct identification.