How Black Lights Work

Black lights may look just like normal fluorescent lamps or incandescent light bulbs, but they do something completely different. Switch one on, and white clothes, teeth and various other things glow in the dark.

If you turn on a black light bulb in a dark room, what you can see from the bulb is a purplish glow. What you cannot see is the ultraviolet light that the bulb is also producing.

Our eyes can see visible light in a spectrum ranging from red through orange, yellow, green, blue and violet. Above violet is ultraviolet light, which we cannot see. A black light bulb produces UVA light (as opposed to UVB light, which is much more harmful).

What you see glowing under a black light, whether on a fluorescent poster or an invisible hand stamp or a newly washed white T-shirt, are phosphors.

A phosphor is any substance that emits visible light in response to some sort of radiation. A phosphor converts the energy in the UV radiation from a black light into visible light.

Keep reading to find out exactly how black lights work, why black lights make some objects glow but not others, and interesting black light applications. Continue…