Exitance is defined as the power per unit area that is emitted from the surface of an object. for a blackbody radiator, the exitance emitted is dependent upon its temperature. calculate the exitance in w/cm^2 for a blackbody radiator at 66 k and 317 k.

Explanation:

For black body radiation, we shall apply Stefan's law, which is defined as follows

E = σ Τ⁴

The value of σ which is also known as stefan's constant is .567 x 10⁻⁷ m⁻²k⁻⁴

and T is absolute temperature. E is heat energy emitted from the surface of a black body per unit area per second.

At temperature 66k

E = .567 X 10⁻⁷ X (66)⁴

= 1.897 X 10⁷ X .567 X 10⁻⁷

= 1.076 J /s m²

1.076 x 10⁻⁴ J s⁻¹ cm⁻²

exitance = 1.076 x 10⁻⁴ Wcm⁻²

Similarly we can calculate exitance of black body  at 317 K as follows

E = .567 X 10⁻⁷ X (317)⁴

= .567 X 10³ Wm⁻²

exitance = .567 x 10⁻¹ W cm⁻⁴