From Longman Dictionary of Contemporary Englishlight on/upon something phrasal verb literary1 SEEto notice or find something by chance His eye lit on a ruby ring. I thought I might have lit upon an ancient manuscript.2 DOWNif a bird or insect lights on something, it stops flying and stands on it → light→ See Verb table
Examples from the Corpus
light on/upon • He left all the lights on.• If you are leaving your caravan at night, leave a light on.• He's too light on his feet.• The baker and the newsagent were open and there was a light on in the Carabinieri station that stood between them.• First, that the particles or riders must seemingly go faster than light on occasion.• I was light on the skids, the troops were out.• In fact, there have been a few carefully done pieces of relevant research that shed some light on the subject.• It's a dance designed for fat people who are not light on their feet. 