Determine the total average hemispherical emissivity and the emissive power of a surface that has a spectral hemispherical emissivity of 0.8 at wavelengths less than 1.5 mm. 0.6 from 1.5 to 2.5 mm, and 0.4 at wavelengths longer than 2.5 mm. The surface temperature is 7777 K.GIVENA surface at temperature (T) = 1111 KSpectral hemispherical emittance (ελ) = 0.8 for λ = 0.6 for 1.5 μm = 0.4 for λ > 2.5 μm (ε3)

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1.0 0.8 0.6 04 0.2 1.5 2.5