The number of photons in a light beam depends on the intensity or brightness of the light, not on the specific wavelength or color. Intensity is determined by the number of photons emitted per second.
In general, visible light sources emit more photons than ultraviolet (UV) light sources of the same intensity. This is because UV light has a higher energy per photon compared to visible light. Since the total energy output of a light source remains constant, the higher energy of UV photons means there are fewer of them to account for the same total energy output.
However, it's important to note that the number of photons per unit of energy (photon energy distribution) is what determines the biological effects of light on living organisms. Even though UV light may have fewer photons, its higher energy per photon makes it more capable of causing biological damage, such as sunburn and potential harm to living tissues, compared to visible light. This is why it's essential to protect yourself from excessive UV exposure, such as wearing sunscreen and using appropriate eye protection.