Solar radiation emitted by sun resembles that emitted by a black body at a temperature of $6000 K$ . Maximum intensity is emitted at a wavelength of about $4800Å$ . If the sun were to cool down from $6000 K$ to $3000 K$ then the peak intensity would occur at a wavelength ....... $\overset{o}{\mathop{A}}\,$
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Two rectangular blocks $A$ and $B$ of different metals have same length and same area of cross-section. They are kept in such a way that their cross-sectional area touch each other. The temperature at one end of $A$ is $100°C$ and that of $B$ at the other end is $0°C$ . If the ratio of their thermal conductivity is $1 : 3$ , then under steady state, the temperature of the junction in contact will be ........ $^oC$
One end of a thermally insulated rod is kept at a temperature $T_1$ and the other at $T_2$. The rod is composed of two sections of lengths $l_1$ and $l_2$ and thermal conductivities $K_1$ and $K_2$ respectively. The temperature at the interface of the two sections is
A body cools from ${50.0^o}C$ to ${49.9^o}C$ in $5\;s$. How long will it take to cool from ${40.0^o}C$ to ${39.9^o}C$? Assume the temperature of surroundings to be ${30.0^o}C$ and Newton's law of cooling to be valid ....... $\sec$
Three discs $A, B$ and $C$ having radii $2\; m, 4\;m,$ and $6 \;m$, respectively are coated with carbon black on their outer surfaces. The wavelengths corresponding to maximum intensity are $300\; nm, 400\; nm$ and $500\; nm$, respectively. The power radiated by them are $Q_A,Q_B$ and $Q_C$ respectively.
Liquid cools from $50^oC$ to $45^oC$ in $5\ minutes$ and from $45^oC$ to $41.5^oC$ in the next $5\ minutes$.The temperature of the surrounding is ......... $^oC$
The radiant energy from the sun incident normally at the surface of earth is $20\, \frac{{k\;cal}}{{{m^2}\;min}}$. What would have been the radiant energy incident normally on the earth, if the sun had a temperature twice of the present one ....... $kcal/m ^2 \,min$