Three discs $x, y$ and $z$ having radii $2 \ m, 2 \ m$ and $6 \ m$ respectively are coated on their outer surfaces. If the wavelengths corresponding to the maximum power radiated by them are $3 \ \mu m, 4 \ \mu m$ and $5 \ \mu m$ respectively,then which of the following is true regarding the power radiated $(P)$?

Power radiated by a black body at temperature $T_1$ is $P$ and it radiates maximum energy at a wavelength $\lambda_1$. If the temperature of the black body is changed from $T_1$ to $T_2$, it radiates maximum energy at a wavelength $\frac{\lambda_1}{2}$. The power radiated at $T_2$ is (in $P$)

$A$ heated body emits radiation which has maximum intensity at frequency $f_m$. If the temperature of the body is doubled,then:

$A$ thin piece of thermal conductor of constant thermal conductivity,insulated on the lateral sides,connects two reservoirs which are maintained at temperatures $T_{1}$ and $T_{2}$ as shown in the figure. Assuming that the system is in a steady state,which of the following plots best represents the dependence of the rate of change of entropy on the ratio $T_{1} / T_{2}$?

$A$ wall with a cavity consists of two layers of brick separated by a layer of air. All three layers have the same thickness,and the thermal conductivity of the brick is much greater than that of air. The left layer is at a higher temperature than the right layer,and a steady-state condition exists. Which of the following graphs correctly predicts the variation of temperature $T$ with distance $d$ inside the cavity?

Three identical rods $AB$,$CD$ and $PQ$ are joined as shown. $P$ and $Q$ are midpoints of $AB$ and $CD$ respectively. Ends $A, B, C$ and $D$ are maintained at $0^{\circ} C, 100^{\circ} C, 30^{\circ} C$ and $60^{\circ} C$ respectively. The direction of heat flow in $PQ$ is