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Understanding Infrared Thermography Reading 3

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The Stefan-Boltzmann law: W= σƐT 4<br />

Where:<br />

W = radiant flux emitted per unit area (W/m 2 )<br />

Ɛ = emissivity (unity for a blackbody target)<br />

σ = Stefan-Boltzmann constant= 5.673 x I0 -8 W/m -2 ∙K -4<br />

T = absolute temperature of target (K)<br />

(Comments: for blackbody Ɛ=1, α=Ɛ.)<br />

illustrates that W, the total radiant flux emitted per unit area of surface, (the<br />

area under the curve) is proportional to the fourth power of the absolute<br />

surface temperature T 4 . It is also proportional to a numerical constant σ, and<br />

the emissivity of the surface, Ɛ.<br />

Charlie Chong/ Fion Zhang

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