Question

S.I. unit of emissive power of a body at a given temperature is

• A. $\dfrac{J}{m^2 s}$
• B. $\dfrac{J}{m^2}$
• C. $\dfrac{J}{s}$
• D. $\dfrac{W}{m}$

Hint:

Emissive power always involves both area and time in its unit.

Answer 1

The Correct Option is A

Step 1: Define emissive power.
Emissive power is defined as the radiant energy emitted per unit area of a surface per unit time.
Step 2: Write dimensional meaning.
\[ \text{Emissive power} = \dfrac{\text{Energy}}{\text{Area} \times \text{Time}} \] Step 3: Identify SI unit.
\[ \text{SI unit} = \dfrac{\text{Joule}}{m^2 \cdot s} \]