Three objects colored black,gray,and white can withstand hostile conditions up to $2800\,^oC$. These objects are thrown into a furnace where each of them attains a temperature of $2000\,^oC$. Which object will glow brightest?

For a perfectly black body,the coefficient of emission (emissivity) is:

Select the incorrect statement.

$A$ 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?

The following figure shows two air-filled bulbs connected by a $U$-tube partly filled with alcohol. One bulb is painted black and the other is painted white (or silver/shiny). What happens to the levels of alcohol in the limbs $X$ and $Y$ when an electric bulb placed midway between the two bulbs is lighted?

$A$ body,which emits radiations of all possible wavelengths,is known as