There rods of the same dimensions have thermal conductivities $3K, 2K$ and $K$. They are arranged as shown in fig. with their ends at $100\,^oC, 50\,^oC$ and $20\,^oC$. The temperature of their junction is……. $^oC$

Assuming the sun to be a spherical body of radius $R$ at a temperature of $T$ $K$, evaluate the total radiant power, incident on earth, at a distance $r$ from the sun- (when radius of earth is $r_0$)

A wall is made of two layers of thickness $1\  cm$ and $4\  cm$ and thermal conductivities $K$ and $3K$ respectively. If temperature difference for the wall is $50\ ^oC$ then temperature difference for the thin layer will be

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 $0.25$ ?

A body cools in a surrounding which is at a constant temperature of $\theta _0$ . Assuming that it obeys Newton's law of cooling, its temperature $\theta $ is plotted against time $t$ . Tangents are drawn to the curve at the points $A(\theta  = \theta _1)$ and $B(\theta = \theta _2)$ . These tangents meet the time-axis at angles $\alpha _1$ and $\alpha _2$ as shown in the graph then