What does the term 'black light' refer to?

The term 'black light' refers to invisible light in the near ultraviolet range. This type of light is not visible to the human eye but is capable of causing certain materials to fluoresce or glow. Black lights are commonly used in various applications, including artistic displays, forensic analysis, and even in some pest control methods, where the fluorescence can help make substances or organisms more visible.

In practical settings, black lights emit long-wave ultraviolet light, which can reveal hidden designs and patterns in materials that react to UV radiation. This property makes them particularly useful in entertainment and scientific fields. The selection of this answer reflects a correct understanding of the nature and properties of black light compared to the other provided choices.