The area of the hole of a heat furnace is $10^{-4} \ m^2$. It radiates $1.58 \times 10^5 \ cal$ of heat per hour. If the emissivity of the furnace is $0.80$,then its temperature is .......... $K$.

If the radiation emitted by a perfect radiator has maximum intensity at a wavelength of $2900 Å$, the intensity of radiation emitted by it is (Stefan-Boltzmann's constant $= 5.67 \times 10^{-8} W m^{-2} K^{-4}$ and Wien's constant $= 2.9 \times 10^{-3} m K$).

The rate of dissipation of heat by a black body at temperature $T$ is $Q$. What will be the rate of dissipation of heat by another body at temperature $2T$ and emissivity $0.25$ (in $Q$)?

$A$ spherical black body of radius $12 \, cm$ radiates $450 \, W$ of power at $500 \, K$. If the radius is halved and the temperature is doubled,the power radiated will be ..... $W$.

The surface of a black body is at a temperature $727^{\circ} C$ and its cross-section is $1 \,m^2$. Heat radiated from this surface in one minute in joules is (Stefan's constant $=5.7 \times 10^{-8} \,W / m^2 / K^4$ )

The heat radiated per unit area in $1\,hour$ by a furnace whose temperature is $3000\,K$ is $(\sigma = 5.7 \times 10^{-8}\,W\,m^{-2}\,K^{-4})$.