A very small sample of an opaque surface is initially at 1200 K and has the spectral, hemispherical absorptivity shown. The sample is placed inside a very large enclosure whose walls has an emissivity of 0.2 and is maintained at 2400 K.

(a) What is the total, hemispherical absorptivity of the sample surface?

(b) What is its total, hemispherical emissivity?

(c) What are the values of the absorptivity and emissivity after the sample has been in the enclosure a long time?

(d) For a 10-mm-diameter spherical sample in an evacuated enclosure, compute and plot the variation of the sample temperature with time, as it is heated from its initial temperature of 1200 K.

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