Lerner Physics

So, last year I blogged my combined AP Physics 1 and 2 class. This year, I'm going to do a #teach180 blog for a AP Physics 1 class. I have a student teacher this year, so I don't know how many days of the teach180 I'll get done this year, but I do want to blog a bit this year.

Today was the first day, and I wanted to get right to the lab. So we started the buggy lab. If you don't know about the buggy lab, Kelly O'Shea has an amazing description. We listed our observations; we figured out we would measure time. I do a lot of this lesson like she does. Thanks, Kelly (as well as Brian Carpenter and Chas Deremer.) 

But then, when they wanted to use metersticks, I told them I couldn't find them. All I could find was a long measuring tape. So we could only measure the position of the car on the measuring tape rather than the distance from the start line. I like this move. We start with position this way. I also don't quite set my students up to get position-time graphs on the first lab. I like to see what they get without much guidance. (Also a Brian & Chas move.) When they all whiteboard their information, and see what a graph can do, the class often agrees that graphs are the best way to see all the information quickly. I like the discussion that comes out of this confusion.

I also learned something about the question "Is the buggy moving at a constant speed?" Some student hear that as "Does the buggy do the same thing every time?" rather than "During one time down the track, does it stay at the same speed during that one trial?" I'm not sure how to avoid that confusion. 

We finished the curriculum! We have more practice to do, and tests, and other such stuff, but the end is in the sight.

We ended with a whimper, not a bang, by talking about neutrinos and half-lives and picking up those last little bits of what's left in modern physics. 

As I look back at the first few blog posts, I notice I used to write a lot more each day. I was at the beginning of the marathon we call a school year and not at the end. I also don't want to give away too much. Not too other teachers, or my students this year, of course, but to future readers of this blog, future students who might look here and know everything. It's a silly reason; I see lots of great physics bloggers talk about their every move in class in detail, with answers. But I shy away from telling too much.

Writing this blog has been worthwhile to me. I'm trying to think about what I'll do next year to keep reflecting on and improving my teaching.

We whiteboarded our last photon model of light questions, and the best part of today was the questions. That seems to be my new theme; their questions are so well-crafted and incisive that they should be celebrated. What are the different ways we can define intensity? Why can't an electron just absorb some of the energy of a photon?

And then we moved to special relativity, and the questions kept coming: How is this related to time travel? How much energy would it take to accelerate me to close to the speed of light? What does it mean that "that astronaut" traveled 0.5 seconds into the future?

Now they want to study a lot more special relativity.

It's more of me talking, and my students asking lots of questions. They love it. I don't really know another way.

The goal was to talk about the different conservation laws for nuclear reactions: number of nucleons, charge, mass-energy.

But it opened up so many other questions, including anti-matter, black holes, and dark matter. I tried my best to answer. The conversations were rich and interesting and the questions were great, but I was the sage on the stage. 

I can't wait until they start reading about all these topics and start teaching me. I'll have to wait to the book project after the AP Exam.

We played around with various different gaseous atomic spectra. They are so interesting! Neon looks so red, and the sample marked "air" has so many different lines. We took some artful photos through our cameras, as shown above.

We didn't get quantitative with our observations; I wasn't sure if it was even going to work, but I think next year we can get quantitative. The lines are bright and easy to see, even through cheap diffraction gratings.

We are definitely finishing the year, and, just like last year, when we get to the end of the year, the questions about quantum mechanics are good. Quantum mechanics is weird. I try to explain, and I also try to postpone. I'm not a quantum mechanic!

So, I'm finding the end of the year coming, and I'm actually in a good place. We're going to finish early. We'll have lots of time to review.

I don't think I've ever had that thought before. 

We talked about atomic emission spectra. Of course, I didn't have the tubes ready today (I'll have them tomorrow) so we didn't get to do a lab with it. Still, I could show pictures of the sun's spectrum and its dark lines.

We figured out how to model atomic transitions. The best question was about how this model is similar to and how it different from the model of the photoelectric effect. We talked a lot about the differences of the atoms and what happens to the electron. 

Today was very teacher-centric. I don't know how I feel about this. For one, this is difficult stuff to conceptualize, and for me to be there, introducing parts of it here and there and letting them try some problems about it, works better. They have some pretty strong models on the electric force and on waves that we can build on. I also feel shakier about this unit, which I abbreviate PMAM (the particle model of all matter), than any other unit this year.

I know I could make it more modeling-friendly. I could give them results to experiments and have them come up with explanations. But what those experiments look like, and what makes the data seem real rather than just words on a sheet of paper, isn't clear to me yet. 

It's okay that I'm not done with this unit. I can see the improvements I can make in previous years. It's not like this year isn't successful. The derivation of the Bohr atom went smoother this year than ever before. But there's still more to do to perfect my practice.

What can we explain with light as a ray, as a wave, and as a particle? Let's whiteboard!

So which one is light, really?

Now I get to blow their minds. None of these models works perfectly. We have to make a kludgy wave-particle hybrid called a photon.

It ends in tears.

But then I made it all better when I said we can energy bar charts (LOL diagrams!) to explain the photoelectric effect. I'll show some whiteboards for that tomorrow.

I need to build a lab for this. But, when I don't have a lab, it always seems that PHeT is there. And I'd use the PHeT simulation for this every year just because it makes it so much easier to visualize.

I always start the photoelectric effect by talking about Einstein's Nobel Prize, and the papers he wrote in 1905. I misspoke today, thinking that Einstein's work on the specific heat of metals was published that year. It wasn't, but his work on Brownian motion was that year instead. That makes that year even more amazing in my opinion.

We then experimented with what changed about the current as we changed the intensity and the wavelength of the incident light. We also investigated what happens when we change the voltage applied across the gap. Our results seemed weird until we came up with the quantum hypothesis.

Yes, we played more with diffraction gratings, and we saw great patterns by just using one white light source (see above for three enthusiastic students' pictures of the diffraction). We also played with an electric rotator and strobe light bought long before I ever taught at this school. It's fun to play with persistence of vision. And we did clean up the mess of the back of my room.

But, more importantly, we talked about academic honesty and standards-based grading. Academic honesty is becoming an issue at our school. Students are driven to do well, feel pressure to do well, and will often do almost anything to get a good grade. But, my students said, with my grading system, the focus was on understanding and not doing. I then asked them for help about how I should tweak the grading scale for AP Physics 1 next year, and, with their help, we came up with this outline:

There are four levels, and a student progresses through the levels sequentially.

Level 1: Earned if a student was in class and did the labs and participated in some way in going over the problems

Level 2: Earned by getting a "Quick Quiz" 100% correct. I'll write many versions over the summer. They're designed to be feedback, to see if a student understands the major ideas of the standard.

Level 3: Earned by doing well on a problem in the wild. I will no longer tell them a reassessment is "for this standard." The students must find a problem in the wild, on a longer assessment, and use that standard correctly, along with other ideas.

Level 4: Earned by showing mastery, either through particularly elegant solutions, using the idea over time, or solving difficult problems. This level is the least fleshed out at this point.

I also imagine you can't pass the class without earning at least level 1 on each standard and can't get above a D+ without earning at least level 2 on each standard. At least that's where I am now. Of course, any and all feedback is welcomed for this idea, which I remember seeing in some form on Matt Owen's blog.