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Welcome to our Physics lesson on Wien's Law, this is the fifth lesson of our suite of physics lessons covering the topic of Thermal Radiation. Photon as the Quantum of Light, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
This law gives the relationship between the characteristic wavelength λm of thermal radiation emitted by a black body and the body temperature. This relationship is an inverse variation given by the equation
where b = 2.9 × 10-3 m · K is known as the Wien's constant.
Wien's Law is otherwise known as the "law of displacement" to point out the fact that the value of characteristic wavelength λm "shifts" towards smaller values when the temperature of radiating body increases.
Calculate the wavelength of EM radiation which gives the main contribution in the transportation of energy in the form of thermal radiation emitted by the human body, given that the normal body temperature of a healthy human is 37° C.
Clues:
T = 37° C = (37 + 273) K = 310 K = 3.1 × 102 K
(b = 2.9 × 10-3 m · K)
λm = ?
From the formula of Wien's Law, we have
From the values of EM spectrum given in tutorial 11.6, it is clear that this wavelength belongs to infrared spectrum. We are not able to see this radiation but we only can "feel" it in the form of heat.
You have reached the end of Physics lesson 19.1.5 Wien's Law. There are 6 lessons in this physics tutorial covering Thermal Radiation. Photon as the Quantum of Light, you can access all the lessons from this tutorial below.
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