Wien’s displacement law in blackbody radiation

Learn about Wien’s Displacement Law in blackbody radiation, which describes the relationship between temperature and wavelength of maximum intensity.

Wien’s Displacement Law in Blackbody Radiation

Blackbody radiation is the electromagnetic radiation emitted by an object that is perfectly black and absorbs all incident radiation. These objects are considered to be ideal radiators and absorbers of thermal radiation, and their properties are defined by their temperature. One of the important laws governing blackbody radiation is Wien’s Displacement Law.

The Law

Wien’s Displacement Law states that the wavelength of the maximum intensity of blackbody radiation is inversely proportional to the absolute temperature of the object. Mathematically, it can be expressed as λ_maxT = b, where λ_max is the wavelength of maximum intensity, T is the absolute temperature, and b is a constant known as Wien’s displacement constant, equal to 2.8977729 × 10^−3 m·K.

This law was first formulated by the German physicist Wilhelm Wien in 1893, and it is considered to be one of the three main laws governing blackbody radiation, alongside Planck’s Law and Stefan-Boltzmann Law.

Implications and Applications

Wien’s Displacement Law has several important implications in physics and engineering. One of the most significant is that it allows us to determine the temperature of a blackbody object by measuring the wavelength of its maximum intensity of radiation. This is because the wavelength of maximum intensity is directly related to the temperature of the object, and vice versa.

Another important application of Wien’s Displacement Law is in the field of infrared thermography, which involves the use of thermal imaging cameras to detect and measure the infrared radiation emitted by objects. By measuring the wavelength of the maximum intensity of radiation emitted by an object, the temperature of the object can be determined using Wien’s displacement constant. This technique is widely used in industrial and medical applications, such as detecting hot spots in electrical equipment, monitoring body temperature, and detecting skin cancers.

In addition, Wien’s Displacement Law has implications for astronomy, as it can be used to determine the temperature of stars and other celestial objects by analyzing their spectra. By measuring the wavelength of the maximum intensity of radiation emitted by a star, astronomers can estimate its temperature and other properties.

In conclusion, Wien’s Displacement Law is an important law governing blackbody radiation, and it has numerous implications and applications in physics, engineering, and astronomy. Its discovery by Wilhelm Wien more than a century ago paved the way for many advances in our understanding of thermal radiation and its properties.

Limitations and Extensions

While Wien’s Displacement Law is a useful tool for understanding blackbody radiation, it is important to note that it has certain limitations. One of the main limitations is that it only applies to ideal blackbody radiators and not to all real-world objects. In reality, most objects are not perfect blackbodies and do not emit radiation in a manner that can be accurately predicted by Wien’s Law.

Furthermore, Wien’s Displacement Law only applies to the wavelength of maximum intensity and does not provide information on the entire spectrum of radiation emitted by an object. Planck’s Law, which is based on quantum mechanics, provides a more complete description of blackbody radiation and can be used to determine the full spectrum of emitted radiation.

Despite these limitations, Wien’s Displacement Law remains an important concept in the field of thermal radiation and has found numerous applications in a variety of fields.


Wien’s Displacement Law is a fundamental law of physics that describes the relationship between the temperature and the wavelength of maximum intensity of blackbody radiation. Its discovery has had numerous practical applications in fields ranging from infrared thermography to astronomy, and it remains an important concept in the study of thermal radiation. While it has certain limitations, it continues to be an important tool for understanding and analyzing the properties of electromagnetic radiation emitted by objects.