Welcome to the forum. The only reason frogs require a light source would be as a form of heat. Generally, amphibians do not need UV light to make Vitamin D like reptiles do. I use a normal incandescent light bulb to raise the pacman terrarium during the day, but I have a heat mat set to warm it all the time (the idea is that it's warmer during the day due to two heat sources and colder at night because there's only one then. Pacman frogs are sensitive to periods of temperature below about 21 degrees C (70 F), as I was reminded a few days ago when I lost one due to cold stress - we moved from a warm place to a cold place in September and I hadn't quite realised how seriously intolerant of cooler temperatures Pacman frogs are.