The following figure shows a metal cylinder, containing boiling water. One half side A is polished and another half, B is painted black. Two thin metal sheets X and Y are painted black and have one rubber stopper fixed with wax on each sheet. These sheets are equidistant from the boiling water (container A, B) as shown in the diagram. What would you expect to happen after a few minutes? Give a reason for your answer.
Solution
After a few minutes, the rubber stopper fixed to plate y will drop down because the plate y is on the black side of the cylinder. The black side of the cylinder radiates more heat than the polished side so it heats up the plate Y faster than heating up of plate X by polished surface of the cylinder which melts down the wax holding the stopper and the stopper will drop down
