We know that, when a parallel beam of light which may parallel to principal axis is incident on the concave mirror then after reflection the light rays converges at focus or at a point in the focal plane.
Due to the converging property of concave mirror they are mostly used in solar devices.
In solar devices, the parallel beam of rays which are coming from the sun are converged and focused at a point in the focal plane of concave mirror. Due to which at that point large amount of heat is generated which is used for many purposes such as to produce electricity, for cooking also.
Hence, due to the converging property of concave mirror they are used in solar devices.
