Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Solar Heating

Objective

The black colored surface absorb and radiate more heat.

Apparatus

Thermometer, two containers — one painted with white color and other with black color

Procedure

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Take two cardboard boxes of the same size. Paint the inner walls of one white and paint the other black. Cover the top of the box with glass and keep the boxes in the sun. The glass tops will allow sunlight to enter the boxes. After 15 minutes or so, check the temperature of each box. You will find the box with black inner walls is at a higher temperature.

Alternate: You can also do this activity by painting outer walls of cold drink cans.

Discussion

A black body absorbs more radiation energy than a white body. A white body reflects radiations of all colors of light whereas a black body absorbs radiations of all colors.