A radiator emits its maximum hemispherical spectral emissive power at λ max = 2.07 µm. Estimate its temperature T and its emissive power M(T), under the assumption that it radiates like a black body...

A radiator emits its maximum hemispherical spectral emissive power at λ_max
= 2.07 µm. Estimate its temperature T and its emissive power M(T), under the assumption that it radiates like a black body

What temperature does a black body need to be at, so that a third of its emissive power lies in the visible light region (0.38 µm ≤ λ ≤ 0.78 µm)?