ANSWERS: 1
  • Black lights are used for a variety of purposes, including forensics, engineering, mechanical repair, forgery detection and entertainment. The components of a black light are simple and almost identical to those of a standard white light bulb.

    Identification

    The wavelength of the ultraviolet light given off by a black light typically falls in the range of 350 to 375 nanometers. It is just below the range that human eyes can detect unaided, which is 400 nanometers.

    Glass Tube

    The external surface of a black light is a glass tube. The glass is dyed to a specific color to block nearly all visible light, while allowing ultraviolet (UV) light to pass through.

    Inside the Tube

    Black lights contain a near vacuum inside the glass tube, with mercury vapor contained in this vacuum. When the mercury gas is energized, it glows.

    Frequencies

    Although mercury gas gives off green, blue and violet frequencies in addition to the ultraviolet frequency, the UV light is the only one that can pass through the glass. If the UV light reaches any materials that contain phosphor, the materials will reflect the light and glow.

    Fun Fact

    Although they produce such different results, standard fluorescent black lights are nearly identical to standard fluorescent white light bulbs. The only difference between the two bulbs is that white light bulbs are coated with a phosphorous coating, while black light bulbs are simply made of dyed glass.

    Source:

    MadSci Network: What Gases Are In A Black Light Bulb and How Does It Work?

    What-Is-What: What Is A Black Light?

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