Ok I'm totally out of my depth here as I'm only a student but I'm confused about the relationship between the emissivity and black-body characteristics of tungsten. I'm not sure if my fundamental understanding of the topics is incorrect but here is my research:

Spectral emissivity is the ratio of energy radiated from a real material's surface compared with that radiated from a perfect black-body at the same temperature, wavelength and observing angle. The closer this ratio is to one, the closer the material is to a good black-body

Tungsten has a spectral emissivity that averages about 0.4 depending on temperature, age etc.

Tungsten filaments in incandescent lights are very good representations of black bodies.

But how can the spectral emissivity of tungsten be so low but an incandescent bulb be almost a perfect black-body?


According to Stefan-Boltzmann equation(ε =σT^4), emissive power is directly proportional to fourth power of temparature. So,(i) Tungsten has to be heated to very high temparature which is assisted by its high boiling point. According to Wien displacement law(max(λ)=b/T),the maximum frequency of spectral distribution for which the radiation has the greatest intensity is directly proportional to the temparature of the (nearly) black body. But Tungsten has a low average emissive power,so it can emit only low frequency radiation like red and orange on incandescence.


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