Wien displacement law

It discusses Wien displacement law of blackbody radiations. Wien's law explains the inversely proportional relationship of peak wavelength having maximum intensity with an absolute temperature of the body.

Transcript

1. Jayam chemistry adda presents Wien displacement law
2. Wilhelm Wein, in 1893, derived a formula to measure the highest spectral radiance of a blackbody as a function of its wavelength at a particular temperature and is renowned as Wien displacement law. 02
3. Overview It unfolded the shift of peak-intense wavelength towards shorter wavelengths at higher temperatures. Hence, the term 'displacement" implies the movement of crest wavelength to shorter wavelengths. Moreover, the Wien displacement law interprets an inversely proportional relationship of maximum intense blackbody radiation wavelength (λm) with its absolute temperature. And the law held good at shorter wavelengths of radiation emissions but failed to give accurate results at longer wavelengths. Blog:https://jayamchemistrylearners.blogspot.com/
4. Wien displacement law formula The Wien displacement law formula is a temperature-specific empirical relation for the peak-intense wavelength of a blackbody curve. λm x T = b Where, λm denotes the wavelength of thermal radiation with peak intensity. T= absolute temperature of the body. b=Wien's constant. The numerical value of Wien's proportionality constant is 2.89 x 10^-3 meter Kelvin, and the alphabet 'b' symbolizes it.
5. Wien displacement law and wavelength With the invention of the mathematical formula, Wien concluded that the product of the zenith wavelength with the body's temperature is always constant in thermal equilibrium conditions. It's possible to quantify the temperature of an object from the radiation wavelength by Wien's law and vice versa. At room temperature, for 25 degrees centigrade, the highest wavelength of intense radiation is 9.6 micrometers.
6. Similarly, for 30 degrees centigrade, the highest wavelength of intense radiation is 9.3 micrometers. Both these examples show that, at room temperature conditions, hot objects emit energies in the infrared region predominantly. When the radiation color is yellow with 550 nm wavelength, its temperature will be 5255 Kelvin, following Wien's formula. Likewise, if the radiation temperature is 7225 Kelvin, it is white-colored with 400 nm wavelength. It contradicts our assumption that red objects are hot and white bodies are cold. White-colored materials possess the highest temperature of all the other colors of visible radiations. Finally, the Wien displacement law graph for the peak wavelength positions of hot material at its absolute temperatures shows a linearly declining curve. Blog: https://jayamchemistrylearners.blogspot.com/
7. Wien displacement law constant The product of λm with the body's temperature on the Kelvin scale is a fixed number called the Wien displacement law constant. λm x T = b It defines the inversely varying relationship of maximum intense hot electromagnetic radiation wavelength with the object's temperature in thermal equilibrium conditions. The numerical value of Wien's proportionality constant is 2.89 x 10^-3 mK, and the alphabet 'b' symbolizes it.
8. Wien displacement law applications What does it do? Wien displacement law deals with the spectral radiance of hot bodies as a function of their wavelengths at a uniform temperature T. This data helps to understand the temperature at which a material can release highly intense radiation. Where is it used? It plays a principal role in designing thermal equipment for heating and medical treatment purposes. Mammals absorb and radiate thermal energies to a large extent in the far infrared regions at room temperature conditions of 25 degrees centigrade to 35 degrees Celsius. So, the temperature of heating equipment is adjusted based on their requirement following Wien law. How will it do? It helps to measure the spectral radiance of emitted thermal radiations by quantifying their absolute temperatures. The sodium spectrum emits two intense yellow-colored D-lines at 588.99 nm and 589.59 nm, indicating peak intensified spectral emissions at approximately 5000 Kelvin temperature.
9. Final thoughts How will it work? It only calculates the maximum intense spectral emissions wavelength released from a hot object at its absolute temperature conditions. It is an approximation relationship to relate a body's highest emissive power with its temperature. What is its limitation? Though, Wien displacement law gives accurate results only for short-range wavelength measurements. It is invalid at longer wavelength radiant emissions at the same temperature conditions. So, it cannot apply to precise measurements of wavelengths of radiation. When will it be used? But in demanding situations, its ease in calculating peak intense wavelengths of thermal electromagnetic radiations with their temperature data makes it convenient.
10. Thank you For multiple choice questions with answers on this topic, kindly visit our blog article at; https://jayamchemistrylearners. blogspot.com/2022/10/quiz-on- wien-displacement-law- chemistry.html