Glow in the Dark

Remember way back when I told you about fluorescence?  Well there is another funny phenomenon called phosphorescence, and it's the secret behind all of your glow-in-the-dark decorations and toys.  You probably even know a little about how they work. 

Think about it.  When you look at the object in the dark, is it always glowing?  Not if you didn't leave it in the lamplight before you turned off your lamp!  That's because you have to "charge" the phosphorescent material up like a battery.  This "charging" happens optically.  Light from your lamp hits the atoms in the material, the atoms become excited and reach what is called a "triplet state," where the upper state lifetime for the atom is quite long (minutes or hours).  There is a bit of quantum mechanics behind it all, but the previous description is just a fancy way of saying the atom is storing the energy for a while before letting it go. 

When many of the atoms are charged, and you turn off the light, some of the atoms start spitting out their energy in the form of light.  This continues to happen until all of the atoms have released their energy.

How does this relate to lasers?  Well a laser can be used to charge a phosphorescent material super fast, since the laser is so intense and blasts all of the atoms in the material to their triplet states.  Check out the video below to see this in action!