A two-color pyrometer is a device that is used to mea sure the temperature of a diffuse surface, T_s. The device measures the spectral, directional intensity emitted by the surface at two distinct wavelengths separated by Δλ. Calculate and plot the ratio of the intensities I_λ+Δλ.e + (λ + Δλ, θ, ∅, T_s) and I_λ.e(λ, θ, ∅, T_s) as a function of the surface temperature over the range 500 K < T_s < 1000 K for λ = 5 μm and Δλ = 0.1, 0.5, and 1 μm. Comment on the sensitivity to temperature and on whether the ratio depends on the emissivity of the surface. Discuss the tradeoffs associated with specification of the various values of Δλ. Hint: The change in the emissivity over small wavelength intervals is modest for most solids, as evident in Figure 12.17.