The velocity of heat radiation in vacuum is

Why are the bottom layers of cooking vessels kept black in color?

Two thermometers $A$ and $B$ are exposed to sunlight. The bulb of $A$ is painted black,but that of $B$ is not painted. Which of the following statements is correct regarding this case?

If Earth did not have an atmosphere,the temperature would be . . . . . . .

Inside a closed furnace held at a temperature of $400\, K,$ we have a black body. $A$ hole of area $10\, cm^2$ is opened in the furnace so that sunlight starts falling on the black body. The intensity of sunlight is $2000\, W/m^2.$ In the steady state:

Good absorbers of heat are