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Many people are curious: isn’t ultraviolet light invisible? How come we can still see violet or blue light when LED UV curing lamps are operating? Is there a problem with the equipment? Here, we need to talk about visible and invisible light. The visible light that the normal human eye can perceive has a wavelength between 780 and 400 nm. Beyond this wavelength, it will not elicit a visual response, meaning it is invisible. So, theoretically, the wavelength of LED UV curing lamps is between 365 and 405 nm, which should be invisible light. So why do we see visible violet or blue light when using LED UV lamps?

This is mainly because ultraviolet light is actually light emitted from the ultraviolet spectrum by the recombination of electrons and holes in LED UV. While emitting ultraviolet light, it also emits visible light in adjacent wavelengths. Therefore, in addition to ultraviolet light, visible violet and blue light can also be seen. This is why LED UV curing lamps emit violet or blue light. Furthermore, the emitted light serves as a reminder that people are under ultraviolet radiation and should not linger unless absolutely necessary, as the ultraviolet light emitted by LED UV belongs to the UVA band, which can penetrate the skin and cause harm.