Question

What is the SI unit of Stefan’s constant?

• A. $W{m}^{-2}{K}^{-4}$
• B. $J{m}^{-2}{K}^{-4}$
• C. $N{m}^{-2}{K}^{-4}$
• D. $J{s}^{-2}{m}^{-2}{K}^{-4}$

Answer 1

The correct option is A

$W{m}^{-2}{K}^{-4}$

The energy of thermalradiation emmitted per unit time by a blackbody of surface area A is given by
$E=\sigma A{T}^4$
where $\sigma$ is a universal constant known as Stefan's constant. Putting the SI units for energy, temperature and area we can arrive at option (a)