The relation between emissivity $e$ and absorptive power $a$ for a black body is:

Which of the following statements does not hold good for thermal radiation?

The Sun emits radiation in all directions. The Earth receives approximately $1.4 \ kW/m^2$ of radiation per second. The distance between the Sun and the Earth is $1.5 \times 10^{11} \ m$. How much mass does the Sun lose per day? $(1 \ \text{day} = 86400 \ s)$

Which of the following statements is true for a perfectly black body?

Three identical metal spheres (of same surface area) have red,black,and white colors and they are heated up to the same temperature. They are allowed to cool. Arrange them from maximum rate of cooling to minimum rate of cooling.

$A$ sphere,a cube,and a thin circular plate,all made of the same material and having the same mass,are heated to the same temperature of $200^{\circ} C$. When these are left in a room,which one reaches room temperature the fastest?