It is estimated that per minute each $cm^2$ of earth receives about $2\ cal (1\ cal = 4.18\ J)$ of heat energy from the sun. This is called Solar constant. In $SI$ units the value is
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The top of insulated cylindrical container is covered by a disc having emissivity $0.6$ and thickness $1\, cm$. The temperature is maintained by circulating oil as shown in figure. If temperature of upper surface of disc is $127^o C$ and temperature of surrounding is $27^o C$, then the radiation loss to the surroundings will be (Take $\sigma = \frac{{17}}{3} \times {10^{ - 8}}W/{m^2}{K^4})$
Two walls of thicknesses $d_1$ and $d_2$ and thermal conductivities $k_1$ and $k_2$ are in contact. In the steady state, if the temperatures at the outer surfaces are ${T_1}$ and ${T_2}$, the temperature at the common wall is
Distance between sun and Earth is $2 \times 10^{8}\, km ,$ temperature of sun $6000\, K ,$ radius of sun $7 \times 10^{5}\, km .$ If emmisivity of the earth is $0.6,$ find out the temperature of the earth in thermal equilibrium (in $k$)
A black body at a temperature of $1640 K$ has the wavelength corresponding to maximum emission equal to $1.75$ $\mu $. Assuming the moon to be a perfectly black body, the temperature of the moon, if the wavelength corresponding to maximum emission is $ 14.35$ $\mu $ is ...... $K$
A black body at $200 K$ is found to exit maximum energy at a wavelength of $14\mu m$. When its temperature is raised to $1000K$ , the wavelength at which maximum energy is emitted is