If the wavelengths of maximum intensity of radiations emitted by the sun and the moon are $0.5\times10^{-6}\, m$ and $10^{-4}\, m$ respectively. The ratio of their temperature is

Two rods of crossectional area $A$ and $2A$ and equal length having thermal conductivities $2K$ and $3K$ are joined in parallel, then equivalent thermal conductivity of their combination will be-

A wall is made up of two layers $A$  and $B.$ The thickness of the two layers is the same, but materials are different. The thermal conductivity of $A$  is double than that of $B.$ In thermal equilibrium the temperature difference between the two ends is $36\,^oC.$ Then the difference of temperature at the two surfaces of  $A$  will be......... $^oC$

Six wires each of cross-sectional area $A$ and length $l$ are combined as shown in the figure. The thermal conductivities of copper and iron are $K_1$ and $K_2$ respectively. The equivalent thermal resistance between points $A$ and $C$ is

The intensity of radiation emitted by the Sun has its maximum value at a wavelength of $510\,\, nm$ and that emitted by the North Star has the maximum value at $350\,\, nm$. If these stars behave like black bodies then the ratio of the surface temperature of the Sun and the North Star is

If the temperature of the sun were to increase from $T$ to $2T$ and its radius from $R$ to $2R$, then the ratio of the radiant energy received on earth to what it was previously, will be