Archimedes is the main person behind this history.
Archimedes burnt the ships of enemies, with the help of sunlight and spherical mirrors i.e. concentrating sunbeams on enemy ships
Spherical mirrors are of 2 types, concave and convex.
Concave mirrors converge the light rays and convex mirrors diverge light rays.
There are several events in history showing that spherical mirrors were generally used to start a fire, spherical mirrors are used in solar cookers ,etc