A furnace wall behaves as a blackbody at temperature K.

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Photodetection, photonic sources and quantum optics · Photodetection, photonic sources and quantum optics

Optics and Photonics, Ch The photon

Problem

A furnace wall behaves as a blackbody at temperature T1=1200T_1 = 1200 K. ((a)) Use Wien's law, λmax⁡T=2.898×10−3\lambda_{\max}T = 2.898\times10^{-3} m K, to find the peak wavelength λ1\lambda_1 of its spectrum. ((b)) The furnace is heated until its temperature doubles, to T2=2400T_2 = 2400 K. Find the new peak wavelength λ2\lambda_2, and give the ratio λ2/λ1\lambda_2/\lambda_1. ((c)) Use the Stefan-Boltzmann law, Me=σT4M_e = \sigma T^4, to find the factor by which the radiant exitance increases when the temperature doubles. ((d)) State, in one sentence, whether the wall's colour or its brightness changes by the larger relative factor.

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