The Photoelectric Effect Explained in Under 4 minutes
Enjoy this video and transcript Karen the Chemistry Rockstar explain the photoelectric effect on her Twitch stream.
In this video you’ll learn that in quantum chemistry the photoelectric effect happens when electrically charged particles are released from a material when it absorbs electromagnetic radiation.
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Okay. How did we know that light could behave as a particle? This goes back to several different experiments that were done. But the one that was really the clincher was an experiment that was devised by Einstein, and this is called the photoelectric effect.
All right. Photoelectric effect, I love because this is the basis for solar cells. And in fact, I have a solar cell right here. It’s on my calculator. My calculator is working because it’s got these little solar panels, and light is hitting it and causing electrons to move.
The photoelectric effect, that is the idea behind it, is that light can come in and hit a surface. So this is light, and notice how I’m drawing this, squiggle line with an arrow, that is one of the designations of light, it is one of the conventions.
And we can also add an H nu right here. This is nu, it looks like a V, it looks like a fancy V. But it is the Greek symbol nu or N. And this is corresponding to frequency. So this is saying that light is corresponding to the energy of light, is Plank’s constant, H, times the frequency of that light. And then we acknowledge that it is a wave because of the squiggle here. And this arrow here shows the directionality of it.
So we have this photon that comes in and it hits this surface. So this surface here, when these experiments were first done, these were done on metals. And so we imagine that this is a piece of aluminum, for example, and light of enough energy was able to eject an electron out of that surface of that metal. So what was noticed, as a series of experiments were done, where it was a one-to-one ratio of a photon to an electron.
The details of that, they’re all laid out in your textbook. It’s really, really cool actually, how they did that. But they determined, all these physicists back in the day.
This is the early 1900s. They determined that even if they poured in a whole bunch, just shone a lot of red light on a surface, those electrons weren’t coming off. But if it was enough energy, maybe violet light or ultraviolet light, then when it hit, electrons would come off.
And it was in this one-to-one ratio. And once they determined this whole idea, clenched this concept that yes, light could also behave as a particle. So photoelectric effect was the experiment that showed that. And what we call light, that is a particle, we call it a photon.
This concept has a lot to do with our atomic structure and a lot to do with how we came to understand what the structure of the atom is.