Kirchhoff's Law of Radiation

A planet of radius $R_p$ is revolving around a star of radius $R^{*}$, which is at temperature $T^{*}$. The distance between the star and the planet is $d$. If the planet's temperature is $f{T}^{\star }$, then $f$ is proportional to

Relation between emissivity $e$ and absorptive power $a$ is (for black body)
 

Which of the following laws is concludes "Good emitters are good absorbers" 

In the adjoining figure, a cell of emf $2 \mathrm{V}$ and negligible internal resistance is connected across a network of resistors. If the resistance of the voltmeter is $80 \mathrm{ohm}$, then the reading of voltmeter will be 

The five rods shown in the figure are of same dimensions. They have thermal conductivities, ${\mathrm{k}}_1$,${\mathrm{k}}_2,{\mathrm{k}}_5,{\mathrm{k}}_4$ and ${\mathrm{k}}_3$. If the points $\mathrm{A}$ and $\mathrm{B}$ are maintained at different temperatures, no heat flows through the central rod if-

"Spectral line of the emission is same as that of the absorption" is the statement of

The temperatures of two bodies $A$ and $B$ are $727°\mathrm{C}$ and $327°\mathrm{C}$, respectively. The ratio $H_{\mathrm{A}}:H_{\mathrm{B}}$ of heat radiated by the bodies is

Assertion: When a green glass is heated in a furnace and taken out, it is found to glow with red light.

Reason: Red and green are complementary.

A body has same temperature as that of the surrounding. Then

Three objects coloured black, gray and white can with stand hostile conditions at $2800°\mathrm{C}$. These objects are thrown into furnace where each of them attains a temperature of $2000°\mathrm{C}.$ Which object will glow brightest?

"Good emitters are good absorbers" is a statement concluded from

From Kirchhoff's law the ratio of emissive power and absorption power of all bodies -

Two bodies $A$and $B$ having temperatures 327$℃$ and 427$℃$ are radiating heat to the surrounding. The surrounding temperature is 27$℃$ . The ratio of rate of heat radiation of $A$ to that of $B$ is

Two spheres of radii 8 cm and 2 cm are cooling. Their temperatures are 127$℃$ and 527$℃$ respectively. Find the ratio of energy radiated by them in the same time

"Good emitters are good absorbers" is a statement concluded from

"Good emitters are good absorbers" is a statement concluded from

"Good emitters are good absorbers" is a statement concluded from

Two plates identical in size, one of black and rough surface (${\mathrm{B}}_1$) and the other smooth and polished (${\mathrm{A}}_2$) are interconnected by a thin horizontal pipe with a mercury pellet at the centre. Two more plates ${\mathrm{A}}_1$ (identical to ${\mathrm{A}}_2$ ) and ${\mathrm{B}}_2$ (identical to ${\mathrm{B}}_1$) are heated to the same temperature and placed closed to the plates ${\mathrm{B}}_1$, and ${\mathrm{A}}_2$ as shown in the diagram. The mercury pellet

A vessel is partly filled with a liquid. Coefficients of cubical expansion of material of the vessel and liquid are ${\gamma }_{\text{V}}$ and ${\gamma }_{\text{L}}$, respectively. If the system is heated, then volume unoccupied by the liquid will necessarily

In the circuit shown, the value of $R$ in ohm that will result in no current through the $30 \mathrm{V}$ battery is: