7th Class Science Heat Absorption of Radiant Heat

     Absorption of Radiated Heat

Every object absorbs more or less heat from atmosphere or from other heat producing sources. If we put anything in the sunlight, after some time it gets heated. The amount of heat to be absorbed by a body depends on its heat absorption capacity. It also depends on the amount of heat produced by the body. On the surface of the Earth, various colors are available. The heat absorption capacity of every object depends on its color also. Black color absorbs more heat than oth.er colors. White color reflects more heat than others. The objects having dark color absorb more radiated heat than the objects of light color.

In the figure below, there are two coffee cans taken for an experiment to show the absorption of radiant energy. Thermometers inside the coffee are used for the measurement of temperature. Now paint the coffee can by white and black color. After some time, we will see that the reading of the thermometer, which has been put inside the black coffee can, is increased. The thermometer inside the white coffee can will also show an increased reading, but it is very low in comparison to that of black polished coffee can. This experiment proves that the black colour of coffee has absorbed more heat than the white one.

Look at the following picture of absorption of heat energy

People prefer to wear white colour during the hot summer session, as the white color of the clothes reflect more heat than other colours. Our house should be painted with light color, because it reflects more heat and protects us from warm summer session. Absorption of heat by the solar cooker is used to cook the food. The inner surface of the water heater is painted with the black colour because of its good absorption capacity of heat.

      Which one of the following colours is good but a poor absorber of heat?

(a) Blue

(b) Red

(c) Light color

(d) Dark color

(e) None of these

Answer: (c)