Which light source is known to harden some light-cure gels?

The correct choice, ultraviolet light, is recognized for its ability to harden light-cure gels used in manicure and nail enhancements. This process is facilitated by the photoinitiators present in the gel formula, which are activated by the specific wavelengths emitted by UV light. Once exposed to UV light, these photoinitiators undergo a chemical reaction that leads to the formation of a solid structure, resulting in the hardening of the gel.

Incandescent and fluorescent lights do not emit the specific wavelengths required to activate the photoinitiators effectively, making them unsuitable for hardening light-cure gels. Halogen light, while emitting a broader spectrum of light, may not provide the same intensity or wavelengths as ultraviolet light to achieve the desired curing effect on these gels. Therefore, ultraviolet light is the preferred and effective light source for this purpose.