Fluorescent lights create ultraviolet light, which is converted to white light, when these UV rays hit the phosphor coating on the glass walls. Leave out the phosphor coating and you have a black-light. Hold a ten dollar bill under the black light and you will see a vertical white line. Hold high quality white paper under a black-light and it will glow. Use a white crayon to write an
invisible message on high quality white paper. You can read the message under a black light, because the crayon blocks the paper fluorescence (the X to the right). Wipe liquid detergent over some low quality white (butcher) paper. It will glow under a black-light. This is why your clothes are “whiter than white.” The UV contributes to the whiteness through phosphorescence much like the fluorescent lights. You
may see your clothes glow at night with the illumination from parking lot lights. Finally, look at your driver's license to see what the security guard at the airport sees (three white circular images).