The coefficient of absorption $(a)$ and the coefficient of reflection $(r)$ of a thin uniform plate are $0.77$ and $0.17$ respectively. If $250 \ kcal$ of heat is incident on the surface of the plate,the quantity of heat transmitted $(t)$ is: (in $kcal$)

In the rainy season,on a clear night,the black seat of a bicycle becomes wet because:

At a certain temperature for a given wavelength,the ratio of the emissive power of a body to the emissive power of a black body in the same circumstances is known as:

The graph shown in the adjacent diagram represents the variation of temperature $(T)$ of two bodies,$x$ and $y$,having the same surface area,with time $(t)$ due to the emission of radiation. Find the correct relation between their emissivities $(e)$ and absorptive powers $(a)$.

According to Kirchhoff's law,the ratio of emissive power to absorptive power for all bodies is:

$A$ perfectly black body is placed in an enclosure (furnace) at room temperature. Then: