Question

Two bodies a and b having equal surface areas are maintained at temperatures 10°c and 20°c. the thermal radiation emitted in a given time by a and b are in the ratio

Answer 1

Formula of thermal radiation emitted per unit area is given by
$\bold{E=\sigma T^4}$
Here, σ is a constant known as Stephen's constant.

Let two given bodies a and b having equal surface area are maintained at temperatures 10°C and 20°C .
so, T₁ = 10°C = 273 + 10 = 283K
T₂ = 20 + 273 = 293K

Now, $\bold{\frac{E_1}{E_2}=\frac{T_1^4}{T_2^4}}$
E₁/E₂ = (283)⁴/(293)⁴ = (283/293)⁴ = (0.9658)⁴ = 0.87
Hence, ratio of thermal radiation emitted per unit area of a and b = 0.87