“The History of Light,” Eisa Davis’s poignant, if uneven, tale of love (romantic and family) and loss (ditto). Unfolding on a set dominated by a grand piano and two playground swings, with light bulbs and text-inscribed glass documents dangling overhead (Robert Klingelhoefer designed the scenery), the play chronicles the reunion of two long-lost friends, Soph (the luminous Amelia Workman) and Math (an appealingly geeky Jason Denuszek ” …Celia Wren Washington Post