Solar water heaters use cadmium black as a coating material on copper water pipes. Explain why

Explanation

The copper spiral tubes are generally housed inside a glass box. The surface of the tube is coated with cadmium black. The heat trapped inside the glass box never escapes out. lpstead it gels absorbtd by Lh cadmium black surface. This heat will be conducted by copper. The hot water rises to the top of the reservoir while cold water circulates inside the pipe. The natural pumping of hot water to the top and cold water to the bottom of reservoir is due to convectional water current. Thus cadmium black increases the efficiency of solar water heaters