A sphere and a cube of same material and same volume are heated upto same temperature and allowed to cool in the same surroundings. The ratio of the amounts of radiations emitted will be
$1 :1$
$\frac{{4\pi }}{3}:1$
${\left( {\frac{\pi }{6}} \right)^{\frac{1}{3}}}:1$
$\frac{1}{2}{\left( {\frac{{4\pi }}{3}} \right)^{\frac{2}{3}}}:1$
A heated body emits radiation which has maximum intensity at frequency $f_m$. If the temperature of the body is doubled
A cylinder of radius $R$ made of a material of thermal conductivity $K_1$ is surrounded by a cylindrical shell of inner radius $R$ and outer radius $2R$ made of material of thermal conductivity $K_2.$ The two ends of the combined system are maintained at two different temperatures. There is no loss of heat across the cylindrical surface and the system is in steady state. The effective thermal conductivity of the system is
Which of the following cylindrical rods will coduct most heat when their ends are maintained at the same steady temperatures?
Two ends of roads of length $L$ and radius $r$ of the same material are kept at the same temperature which of the following rod conducts most heat?
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 $2\,T$ and emissivity $0.25$ ?