Physics – 2.3.3 Radiation | e-Consult

The rate of emission of radiation from a solid object is significantly dependent on its surface temperature. According to the principle of blackbody radiation, all objects above absolute zero emit electromagnetic radiation. The intensity of this radiation is directly proportional to the fourth power of the absolute temperature (T). This is expressed by the Stefan-Boltzmann law: P = εσAT⁴, where P is the power radiated, ε is the emissivity (a value between 0 and 1 indicating how effectively the object radiates), σ is the Stefan-Boltzmann constant, A is the surface area, and T is the absolute temperature in Kelvin.

Therefore, as the temperature of the object increases, the emitted radiation becomes more intense. This means the object emits more energy per unit time. At higher temperatures, the peak wavelength of the emitted radiation shifts towards shorter wavelengths (e.g., from infrared to visible light). A blackbody is an idealized object that absorbs all incident radiation and emits radiation solely based on its temperature. Real objects are not perfect blackbodies, but their emissivity value allows us to approximate their radiation behaviour. A higher emissivity means the object is a more efficient radiator.