Demo Overview:
This activity involved going to East High School and performing a physics demonstration. The demonstration I performed showed how the excitation and the deexcitation of electrons can result in a “glow-in-the-dark” effect. To show this, we used red, green, and UV lasers. I thought that this experiment would give the students an interactive experience with physics, since they would flash all the lasers on the glow-in-the-dark paper. Along with allowing them to hypothesize which laser will work and why.
Instructor Notes:
To begin the demonstration, the glow-in-the-dark paper must be taped to the inside of a box. Decorate the box with the provided glow-in-the-dark stars and planets. Place the box on the table/surface being used. To get the best results, attempt to limit the amount of light exposed to the paper by angling the box away from significant light sources or semi-close the box flaps. With the experiment set up, you can begin engaging with students!
As the students come up to the table, I ask them if they have ever heard of or learned about electrons or photons. If not, then I proceed to give them a quick rundown of what each particle is. Then, for everyone, I begin explaining how electrons have energy and if we shine light (aka a photon) on it – we can give an electron enough energy to where it can jump to a higher energy level. This then prompts me to show the lasers and explain the 3 types of lasers I have. I ask them which one’s they believe will give the electrons enough energy to jump an energy level. From my experience, a lot of them said the red laser! Then, I proceed to give them their hypothesized laser (if they guessed red or green), then the red or green laser. If they guess the UV laser, I give them red then green first (Note: Tell them to not shine the UV laser into theirs or anyone’s eyes!). As they begin the experiment, when they shine the red or green laser on the glow-in-the-dark paper, nothing will occur. However, once they shine the UV laser, the paper will begin to glow wherever the light is placed.
Once the answer is known, I explain how the UV laser provides enough energy to excite the electron to the next energy level. However, what we see is not that excitation, but the de-excitation of the electron, aka the electron jumping back down a level. The electron loses energy as it falls down a level, and that is the light we are seeing right now!