You’ve probably heard of fluorescent lights. Well, now you know what makes them light. The bulb contains a gas that emits ultra-violet (UV) light when it is turned on. That UV light makes the coating on the glass glow. And, if you’ve seen the inside of a tanning booth, you’ll probably notice that those bulbs they use, look a lot like fluorescent light bulbs. Well, they are, they just use a different type of glass – one that lets the UV light through.