Apply Wien’s and Stefan’s laws to analyze radiation emitted by a blackbody
Explain Planck’s hypothesis of energy quanta
Thermal Radiation
Stephan’s Law relates the intensity (I) of the emitted thermal radiation to the temperature (T) of the object
𝜎 = 5.67037 × 10−8 W∕m2⋅K4
Wein’s Displacement Law relates the temperature (T) of the object to the peak wavelength of the emitted thermal radiation
Practice!
Practice 3.1.1
Your temperature is 98.6°F. Assuming your skin is a perfect radiator (e = 1), determine the wavelength corresponding to the largest intensity.
A. 8.0 µm
B. 9.3 µm
C. 3 µm
D. 5.7 µm
E. 29.4 µm
Check your answer: B. 9.3 µm
Discuss!
In what region of the electromagnetic spectrum do room-temperature objects radiate? What problems would we have if our eyes were sensitive in that region?
How does the total intensity of thermal radiation vary when the temperature of an object is doubled?
Physics Education Research at UNG 