Take two aluminium containers. One painted with black and the other with original colours. Fill them half with water and keep them under the sun. Each one should have a lid and thermometer.Note the temperatures in both the thermometers. Initially both of them will show the same temperature. Later, the thermometer inserted in the blacked can will show higher temperature. The difference between the readings will increase as time advances. This shows that the black surface absorbs more heat and reflects less as compared with the other can.
Applications of black and white surfaces
Following are some applications of the principle that black surfaces are better abosrbers and radiators than polished surfaces.
The bottom part of cooking utensils is blackened to absorb the heat from the flame more quickly. The upper part of the utensil and the outer surface are kept polished and shining to reduce heat loss due to radiation.
White clothes are preferred for use during summer as they are poor absorbers of heat.
A fire fighting suit is bright and shiny, so that it does not take in a lot of heat energy and the fire fighter is kept cool.
Coffee and tea stay hot longer in a shiny pot than in a blackened one
A light coloured building stays cooler in summer because it reflects most of the heat radiation from the sun. It is also a poor emitter of heat and stays warm in winter.