alight (up)on
1. To land or rest upon something. The large black crow alighted on the telephone wire high above the street. As he walked into the room, his eyes alighted upon a gorgeous woman wearing a red dress.
2. To arrive at a thought or idea. The engineer alighted on a mathematical solution to the problem he'd been trying to solve all week.
alight (up)on someone or something
to land on something; [for a bird or other flying animal] to come to rest on something. (Upon is more formal than on.) A small bird alighted on the branch directly over my head. It alighted upon the branch and began to sing.
alight on
v.1. To come down and settle on something; land on something: I watch the birds alight on the branches outside my window.
2. To discover or arrive at something by chance: The workers alighted on a simple solution to the problem.