With the help of a labelled diagram,explain the construction and working of a solar water heater.

(N/A) Construction: $A$ solar water heater consists of an insulated metallic box painted black from both inside and outside. Inside this box,copper tubes,also painted black,are fitted in a zigzag pattern. The black color is used to absorb the maximum radiant heat energy from the sun. The box is covered with a glass sheet lid to trap sunrays by producing a greenhouse effect. The two ends of the copper tubes are connected to a water storage tank as shown in the diagram. The entire setup is placed on the roof of a building to ensure maximum exposure to sunlight.
Working: When sunlight falls on the solar heater,the radiant heat energy enters the metal box through the glass lid and is absorbed by the water flowing through the copper tubes. As the water gets heated,it expands and becomes less dense,causing it to rise and flow into the storage tank through the upper tube $(R)$. Simultaneously,fresh cold water from the bottom of the storage tank flows into the copper tubes through the lower tube $(Q)$ to replace the heated water. This continuous circulation of water between the solar heater box and the insulated storage tank continues as long as there is sunshine. The hot water stored in the tank can then be drawn out for use through the tap attached to the pipe.