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 north star is
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Four rods of same material and having the same cross section and length have been joined, as shown. The temperature of the junction of four rods will be ............... $^{\circ} C$
At a certain temperature for given wave length, the ratio of emissive power of a body to emissive power of black body in same circumstances is known as
The spectral emissive power $E_\lambda $ for a body at temperature $T_1$ is plotted against the wavelength and area under the curve is found to be $A$. At a different temperature $T_2$ the area is found to be $9A$. Then $\lambda _1/\lambda _2 =$
A hollow sphere of inner radius $R$ and outer radius $2R$ is made of a material of thermal conductivity $K$. It is surrounded by another hollow sphere of inner radius $2R$ and outer radius $3R$ made of same material of thermal conductivity $K$. The inside of smaller sphere is maintained at $0^o C$ and the outside of bigger sphere at $100^o C$. The system is in steady state. The temperature of the interface will be ........ $^oC$
A body cools from $60\,^oC$ to $50\,^oC$ in $10\,minutes$ . If the room temperature is $25\,^oC$ and assuming Newton's law of cooling to hold good, the temperature of the body at the end of the next $10\,minutes$ will be ......... $^oC$
Two spheres $P$ and $Q$, of same colour having radii $8\;cm$ and $2\;cm$ are maintained at temperatures ${127^o}C$ and ${527^o}C$ respectively. The ratio of energy radiated by $P$ and $Q$ is
A metallic prong consists of $4$ rods made of the same material, cross-sections and same lengths as shown below. The three forked ends are kept at $100^{\circ} C$ and the handle end is at $0^{\circ} C$. The temperature of the junction is ............. $^{\circ} C$
Two thermometers $A$ and $B$ are exposed in sun light. The valve of $A$ is painted black, But that of $B$ is not painted. The correct statement regarding this case is