For an opaque surface, the absorptivity $$\left( \alpha \right),$$ transmissivity $$\left( \tau \right)$$ and reflectivity $$\left( \rho \right)$$ are related by the equation:

The following figure was generated from experimental data relating spectral black body emissive power to wave length at three temperatures $${T_1},{T_2}$$ and $${T_3}\left( {{T_1} > {T_2} > {T_3}} \right).$$

The conclusion is that the measurements are

A plate having $$10\,\,c{m^2}$$ area each side is hanging in the middle of a room of $$100\,\,{m^2}$$ total surface area. The plate temperature and emissivity are respectively $$800$$ $$K$$ and $$0.6.$$

The temperature and emissivity values for the surfaces of the room are $$300$$ $$K$$ and $$0.3$$ respectively. Boltzmannn constant $$\sigma = 5.67 \times {10^{ - 8}}\,\,W/{m^2}{K^4}.$$ The total heat loss from the two surfaces of the plate is

The shape factors with themselves of two infinitely long black body concentric cylinders with a dia ratio of $$3$$ are ....... For the inner and ..... for the outer