Question

At 273°C, the emissive power of a perfectly black body is R. What is its value at 0°C?

पर्याय

• `R/4`

• `R/16`

• `R/2`

• None of these

Answer 1

`underlinebb(R/16)`

Explanation:

According to Stefan's rule, the total radiant energy released by a black body per second per unit surface area is inversely proportional to the absolute temperature (T) of the object.

∴ E = σT⁴

where σ is Stefan's constant.

Given, E₁ = R

⇒ T₁ = 273°C = 273 + 273 = 546 K

and T₂ = 0°C = 273 K

∴ `E_1/E_2 = T_1^4/T_2^4 ⇒ E_2 = T_2^4/T_1^4 xx E_1`

⇒ `E_2 = (273)^2/(546)^2R = R/16`