A black light works by producing UVA light, or ultraviolet light.
Ultraviolet light by itself is above the spectrum of visible light, and cannot be seen. However substances that are emitting light in response to radiation (phosphors) glow in the dark in the presents of a black light.
The glow is created by the special way phosphors use the energy from UV light. When a photon from a UV light hits the phosphorous material, it causes the electrons to get excited and stray farther from the nucleus than they normally would. When the electron falls back to its normal state, some of the energy is lost in the form of heat. When the UV light wave is reflected back to the human eye, it now has less energy, therefore a shorter wavelength. This wavelength is in the range that we can see. The end result being, you cannot see the majority of the light coming from the source, but you can see its reflection off of objects containing phosphors.
Black lights are used in crime scene investigators to identify body fluids – including semen, sweat, saliva and urine. Semen happens to glow the brightest.
Turn your phone to a body fluid tracking tool, and detect semen on the go.
1. Apply a small piece of tape over the phone’s flash.
2. Color the piece of tape with the blue Sharpie.
3. Apply another small piece of tape on top of the blue tape, and color it with the purple Sharpie.
Now turn your flashlight app on in a dark motel room and be a appalled.
Enjoy : )