ANS:A - black

The Stefan-Boltzmann law specifically applies to black bodies. A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. It also emits radiation across the entire electromagnetic spectrum. The Stefan-Boltzmann law states that the total energy radiated per unit surface area of a black body is directly proportional to the fourth power of the body's absolute temperature. Mathematically, it's expressed as: 4P=σAT4 Where:

• P is the total power radiated per unit area (in watts per square meter).
• σ is the Stefan-Boltzmann constant (5.67×10−85.67×10−8 W/m²K⁴).
• A is the surface area of the black body.
• T is the absolute temperature of the black body (in Kelvin).

So, strictly speaking, the Stefan-Boltzmann law applies specifically to black bodies. However, in practical terms, it can be used as an approximation for real objects, with some adjustments, especially for objects that are close to black bodies in terms of their absorption and emission characteristics.