Question: Unit of Stefan’s constant is: [PMT/NEET-1989]
a. $ \text{J s}^{-1} $
b. $ \text{J m}^{-2}\text{s}^{-1}\text{K}^{-4} $
c. $ \text{J m}^{-2} $
d. $ \text{J s} $

Answer: b. $ \text{J m}^{-2}\text{s}^{-1}\text{K}^{-4} $

Solution: From Stefan–Boltzmann law $j^{*} = \sigma T^{4}$,

Hence,
$$
[\sigma] = \frac{[j^{*}]}{[T^{4}]} = \text{J m}^{-2}\text{s}^{-1}\text{K}^{-4}.
$$