Q1: While the total emissivity of a perfect black body is unity, the same for a real body is

ANS:D - between 0 and 1

The correct answer is: d) between 0 and 1 Total emissivity (�ε) of a real body is a dimensionless quantity that represents the efficiency with which a surface emits thermal radiation compared to a perfect black body at the same temperature. A perfect black body has a total emissivity of 1, meaning it emits thermal radiation as efficiently as possible at a given temperature. For real bodies, total emissivity can range from 0 to 1, where:

• �=0ε=0 implies that the surface does not emit any thermal radiation (perfectly reflective),
• 0<�<10<ε<1 implies that the surface emits thermal radiation to some extent, but not as efficiently as a perfect black body,
• �=1ε=1 implies that the surface emits thermal radiation as efficiently as a perfect black body.