teaching – dangermouse.net

Pinhole and schlieren imaging

Today I taught two classes this morning. After lunch I went back to Wenona School for another meeting with the Science Club students there. We continued working on the pinhole cameras we built a few weeks ago. At the time we ran out of tracing paper and made two of the boxes with tissue paper instead, which is both more fragile and also less translucent, so it was definitely not as good. Today we had more tracing paper, which we used to replace the tissue paper. We also trimmed one of the other boxes more neatly and stretch the tracing paper more flat across the opening.

After that, I helped start setting up a schlieren photography setup. We mounted a concave mirror on a retort stand with a couple of clamps, and then used a pinhole taped to a xenon bulb light to get a bright beam of light, and found the focal distance of the mirror and focused the light onto a screen next to the light source. For the next step we needed a knife edge and a camera, but time was running out and the lab assistants helping us couldn’t get them in time. So we left the remainder of the setup for next time.

Well be taking a two-week break for the end of term holidays, and then when we come back in three weeks hopefully we can finish it off and take some cool photos of things like the turbulence above a candle flame.

On the way back home I picked up Scully from my wife’s work, and then I had three more classes this evening. A pretty full day!

Atomic theory prep

Today I mostly worked on a lesson plan and presentation for tomorrow’s online science class with my ongoing Outschool student. We’re heading towards basic atomic theory, after don some experiments with chemical reactions, and talking about the early experiments of 18th century chemists like Antoine & Marie-Anne Lavoisier. The goal for tomorrow is to get up to John Dalton’s formulation of atomic theory, and then leave some dangling questions that will lead into atomic structure in future weeks.

I did a 5k run after breakfast, before the day warmed up too much. Sydney reached 27°C today, and was 28°C yesterday – very warm for this early in spring. The mean maximum for September is only 20°C, but the forecast this week sees every day above that.

I went to pick up Scully from my wife’s work at lunch time. On the way I stopped to take a photo of this plant fibre snake thingy that is used to delineate the edge of a path through a park. Someone has put eyes on it, which makes it look amusing.

I stopped in at the local hardware store on the way home to look for that wood offcut I want to make a laundry shelf out of. But unfortunately when I asked to go through their offcuts bin, the guy told me that someone had just come in before me and bought everything that was in there! I looked and it was indeed totally empty. oh well, I’ll just have to keep trying until I find what I want.

Tonight I made calzones for dinner, with spinach and ricotta filling and some tomato sauce to pour over the top. I forgot to add some mozzarella to the stuffing, which I normally do, but they still turned out well.

Student image processing projects underway

Today was the usual busy Monday, with 4 ethics classes in the morning, then a bi of a break before heading into the city for the evening’s image processing session. The lectures are now over and we’re into the student project phase for the next few weeks. This is where most of the work for me is, where I spend the whole evening wandering around, checking how student groups are going, and answering their questions about the project in general or whatever specific image processing thing they’ve decided to work on.

For dinner before the session, I tried a place I haven’t been to before, called Yumko Korean Fried Chicken. They had a “lunch special” bento box which you could also have for dinner, with pieces of fried chicken, salad, rice, and a selection of three appetiser dumplings. It was really good, and very filling.

Making colour combo lighting

Overnight, since yesterday’s post, we added almost 50 mm more rain to make yesterday’s total 122 mm. It was really wet. There was flash flooding in many parts of Sydney, including in our basement garage, but not too serious thankfully. Today it continued raining until about lunchtime, but then cleared up, and the afternoon was sunny, but cold and windy.

After my morning critical thinking classes, I went to Wenona School again to help students out with science projects. We’d finished the pinhole cameras last week, and this week we worked on taping coloured filters over LED stage lights to make coloured lighting. We arrayed the lights and tested various combinations. I showed how red, green, and blue lights combine to make white, and then the students had fun putting their hands in front of them to make coloured shadows as they intercepted the lights coming from different angles. I explained what was happening so they understood the science behind it, and the difference between additive colour mixing (like light) and subtractive (like with paint).

I came home and had three more classes this evening. Another busy day!

Finishing off pinhole cameras

This morning I had two online critical thinking classes. Then after lunch I went to Wenona School to finish off building pinhole cameras with the students – which we began work on last Thursday. I cut out holes for the different sized lenses we had and got the girls to tape the lenses into place, and then add tracing paper as a screen for the projection. We ran out of tracing paper and had to use tissue paper for the last two which turned out to be not as good as it has more texture to it, making the image not as clear. I’m hoping they can replace it with tracing paper.

Here are photos of the resulting cameras:

The largest diameter lens is on the left, stepping down in size to the right. So the projected image should get darker from left to right. It’s a little bit obscured by the fact that boxes 1 and 4 have the tissue paper, which isn’t as translucent as the tracing paper. But overall the project worked really well!

The science head is going to try to get the boarding school girls to take photos of the moon over this weekend when we get a full moon, to use for the 3D stereo effect. Hopefully they can get that achieved properly.

I walked back home, and on the way I passed the shop that has 3D-printed D&D and gaming scenery. It’s always been closed when I’ve walked past before, but today it was open! And there was a guy inside painting scenery. So I popped in to have a look and chat to him. He was happy to have a chat and we talked for several minutes about miniature models and playing D&D. Turns out this guy is also running an Old School D&D game, using the Swords & Wizardry retroclone of the original 1974 D&D rules. So it was cool to swap some stories about our campaigns.

The weather was warm today, reaching 24°C, the warmest day since early May. On Monday the forecast is 27°C!

I got home and taught three more classes in the evening, and baked a sourdough loaf which I’d made earlier. Phew!

Making pinhole cameras

After two online classes in the morning, I did a 5k run today. When I got home I had lunch and then had a shower and left to go in to Wenona School for a second visit to help do science things with the students there.

Today I was working with some Year 8 students, helping them make pinhole cameras, both with open pinholes and also ones with lenses in the hole to focus the light and produce a brighter image. The lab assistant brought out a collection of dozens of lenses, many of which were in paper sleeves marked with diameters and focal lengths. I asked if the focal lengths were likely to be correct and she almost laughed as she said no.

So the first order of business was the find a set of lenses of different diameters with roughly the same focal lengths. We found four different diameter lenses, and there were many of the two middle diameters. We measured the focal lengths by holding them up and using the lenses to focus the view out a window into a sharp image on a white board, and measuring the distance from the board to the lens. Some of the focal lengths were too short, but we found a good set with lengths around 20 centimetres.

Then I got the girls to help cutting cardboard boxes (which held reams of copier paper) to lengths matching the different focal lengths. The lab assistant had brought out Stanley knives to do the cutting because I’d requested some when emailing the science coordinator about equipment. But I realised it might not be a good idea to have 13-year-olds using such knives and called over the coordinator to ask. Lucky I did, because she said that the girls were definitely not allowed to use them. But they could use scissors, so I got them to work cutting boxes with scissors.

I used a Stanley knife myself to cut a circular hole in one to fit one of the lenses, and had some girls use tape to affix the lens in place. Then they taped a sheet of tracing paper over the open end of the box, and we tested it out. The lens projected an upside down image of the view out the window onto the tracing paper and it was nice and sharp! It worked beautifully. This got the girls excited and they played with standing in front of the window and waving their arms while others watched the live image on the back of the box. It was pretty cool.

We ran out of time before completing all the boxes, but the partially complete ones were put on a trolley to be stored away safely for next time, when we’ll finish them off.

I headed home and then in the evening did three more critical thinking classes. Unfortunately, my Internet died during the first one, and I had to hurriedly open Zoom on my iPad (which has 4G) to continue. The second class I ran entirely on my iPad. It worked, but was a bit clunky. I had to hold the iPad in my hand the whole time to get a good camera angle for the video, and I couldn’t share prepared slides I had to illustrate some things. Fortunately the Internet came back in time for the third class. It’s been really flaky this week, dying multiple times on the weekend as well. I don’t know what’s going on with it.

Hopefully it won’t happen again…

Image processing lecture done

Today was a full-on teaching day. Four critical thinking classes filled the morning, up to 1pm.

Then I had lunch, and went for a 5k run. Had a shower, and went over my notes for tonight’s lecture at the University of Technology Sydney. I mentioned last week that the lecturer is away this week and asked me to give the lecture tonight. It was an introduction to machine learning and AI for image processing, and it went really well. Several of the students thanked me as they left afterwards.

Before the lecture I had Thai pad kee mao for dinner at a good place I know near the university. Next week I might try somewhere new, but this week I decided to stick to somewhere I knew had quick service, so I wouldn’t be late for the lecture.

Now time to relax before bed…

Super busy Monday

I started work at 8am, with four critical/ethical thinking classes online. With a break in between that took me up to 1pm, when I had a break for lunch.

Then at 2pm I had another online meeting, this time for Standards Australia where I’m still chairing the Photography committee. I had to report on my attendance at the Berlin ISO meeting back in June, going through all of the technical and administrative discussions there. And some other business related to adopting Australian standards based on international ones.

Then before 5pm I went into the city for this evening’s image processing lecture at UTS. I stopped along the way at a Japanese restaurant near the university to get dinner, and had some gyoza and takoyaki with rice, which was pretty good.

The lecturer is going to be away in two weeks, I learnt today, and he asked if I could fill in and give that week’s lecture. It will be on pattern recognition and machine learning in image processing, the introductory lecture to two further weeks of machine learning algorithms and procedures. This is lecture 5 in the course; in previous years I’ve given lectures 3 and 4, so I’m expanding into later material.

Time to relax before bed with some non-thinking TV…

Fading like a flower

I had a busy Sunday. I really want to get ahead with buffering strips for Darths & Droids but have been unable to since I got back from Europe due to having so many other things to do. But today I managed to make two complete strips from scratch, which gets me one ahead of where I was.

It used up a lot of time though, and ended just before my first critical thinking class this afternoon. Then I had a break during which I cooked dinner, followed by three classes in a row. My brain started to fade halfway thought the second last class, and I was spacing out a bit trying to navigate my list of questions for the kids. I tend to jump around a bit, especially if the kids raise issues that I wanted to address in later questions; I bring them forward and then jump back. So finishing the last two classes was a bit of a struggle. Anyway, I managed to do it, though I wonder if the kids noticed or not.

For dinner I made pasta with pesto, and for added vegetables I used some of a wombok (or Chinese cabbage, or, apparently, napa cabbage, a name I’d never heard before) that I had in the fridge. It worked fairly well. Now I’m thinking of using wombok cooked German-style as a side for spätzle.

When all you have is a wombok, every dish looks like it can use a Chinese side.

Wenona School visit

Today I had two online classes in the morning, then I had to get ready for my visit to Wenona School, during the student lunch break when they had their Science Club meeting. I took a laptop loaded with the slide presentation I made yesterday.

After checking in at reception, I met the head of the science department, who escorted me into the science labs. These are in a very new building, and were super modern. We chatted a bit while waiting for the classes to end and lunch time to begin, then moved into one of the rooms where the girls in the Science Club would assemble. I set up my laptop to project on the screen.

The audience was about twenty girls from I think Years 8 through 11, plus several of their science teachers, and the lab assistant. I did my talk about human vision and cameras, showing the links between the biology and physics and going into details about colour vision and perception. I had to cut short the end to finish on time, since we started a few minutes late (the students were getting lunches and arrived in dribs and drabs).

Then we had question time. The first three questions from students were:

How does colour blindness work? I was happy to hear this, as one of the slides I’d stopped short of was specifically about this, showing how missing one type of cone cell in the eyes can make it impossible/difficult to distinguish red and green
Do we know if people are really seeing the same colours if they look at the same things? Oh my gosh… Believe it or not, this was exactly what another of the skipped slides was about! I moved ahead to that one and explained what we do and don’t know about this idea.
I heard this species of shrimp can see lots more colours than we can; how does that work? Okay, wow. I didn’t specifically have a slide on the mantis shrimp, but I did have one on tetrachromacy in birds, which is essentially the same thing, just not as extreme.

So that was amazing and really good. As the students left, some of them came up to me and said they really enjoyed the talk, and the teachers did too. So over all it was a great success.

The head of science then took me to a quiet room where we could talk about ongoing projects and how I could help. The Year 9 students are doing term projects on light, and could use some ideas and assistance with organising their projects. We ran through some of the fledgling ideas and I offered advice on what was doable and what might be tricky, and gave some suggestions for extending things in different ways. She seemed really happy with that, and our plans to work together this year.

One other thing: I found out their head of science studied physics at Sydney University, and was doing her undergraduate degree when I was doing my Ph.D. So there’s a chance that I actually taught her in the physics labs! Neither of us remembered each other, but it’s highly possible.