Each photon of ultraviolet light has more energy.
Work Step by Step
For photons, E = hf, where E is the energy, h is Planck's constant, and f is the photon's vibrational frequency. A higher-frequency uv photon has more energy than a visible-light photon. A high-energy ultraviolet photon causes particular chemical changes in the skin that even a large number of visible photons cannot accomplish.