For those of you not familiar with black lights … they have the capability of making visible, that which you cannot see with the naked eye.
Counterfeit bills can be easily detected with a black light. Plastic security threads will appear under UV light in legitimate bills, and will glow different colors depending on denomination.
For instance, a $5 bill will be blue, a $20 bill shows up green and a $100 note glows pink.
Forensic investigators also use black lights in crime scenes. Black lights can even show bacteria and germs that you wouldn’t normally be able to see.
A clever YouTuber recently posted a video that shows how you can make your own black light out of your smart phone. All you need is a smart phone, some clear tape, and two sharpies: one purple and one blue.