The absorbed energy is converted to heat energy. The scenario you mention with the LED is very close to the blackbody problem known as the ultraviolet catastrophe.. There is a Wikipedia article about it here. What happens in the situation you described is that the light proof box gets hotter.
Diagnosing rust on geraniums can be a challenge for growers. Rust begins with yellow spots on the underside of the leaves and can rapidly progress with brown fungal spores called pustules in the center of each spot. The pustules are raised up off the leaf surface and feel rough to the touch.
Humidity is essential for your dormant geraniums to survive over the winter. Too dry an environment will kill your dormant geraniums. If you see your geraniums have dried, soak them for two or three hours in a bucket or sink of water, then return them to their bags.umidity is essential for your dormant geraniums to survive over the winter. Too dry an environment will kill your dormant geraniums. If you see your geraniums have dried, soak them for two or three hours in a bucket or sink of water, then return them to their bags.