A solar cooker consists of an insulated metal box which is painted all black from inside. A plane mirror reflector is attached to the box. The food to be cooked is placed in containers which are also painted black from outside. The cooler is placed in the sunlight and the position of the reflector is adjusted in such a way that a strong beam of sunlight falls over the cooker top. These rays pass through the transparent glass sheet and are absorbed by the black box and the containers. The box and the containers absorb maximum amount of infra-red radiations from the sunlight falling on it. As a result the temperature inside the box rises to about 100 and this heat cooks the food in the containers.
The major drawback of all solar heating devices has been that their direction has to be adjusted after short intervals so that they keep of facing the sun.