I remember forwarding funny website links and word docs full of copy/pasted jokes around in emails back in the 90s and early 00s. This was a favorite of mine, having dropped out of an applied physics degree with the memory of the "final straw" optics lab where I lost the will to carry on. The equipment was awful, and I was paired with the clumsiest partner in the world. (During our 3rd year work experience semester, he was the only student who received an entirely negative feedback from his employer with the summary "unemployable" - I believe he caused a fire). Every time i stripped an optic fiber cable and mounted it in front of the laser, it seemed like the entire universe conspired to break the brittle glass core. When we did finally line everything up, happily taking measurements, I too ended up drawing a line through noise. In fact I haven't even read the piece yet, so it's been 15+ years since I've seen it, and I still remember laughing out loud at that line.
Electron band structure in germanium, my ass (2000)
81–88 of 88 posts
Re: Electron band structure in germanium, my ass (2000)
#82You sure it isn’t Schottky diodes formed by the metallic contacts that are interfering with the measurement of the bulk germanium properties? I’d sputter deposit metallic contact regions and solder to those, then maybe compare two different thickness samples and look at the difference in resistivity vs. temperature, essentially de-embedding your fixture.
Could they measure the resistance in two direction, then subtract one from another to isolate the symmetric part?
Possibly, but the OP is probably measuring the equivalent of back-to-back series diodes, which would be very symmetrical (if built on the same process). With soldering though, I’m sure they are not equivalent. As the other poster said, they need Ohmic contacts.
Re: Electron band structure in germanium, my ass (2000)
#83I'm quite sure the author knows more than me, by far, so I'll err on the side of believing them, but I'm amazed that someone could read a physics textbook, but not be able to do a resistance measurement in a way they were happy with.
Anything above microohms would be trivial to measure compared to the skill needed to understand even the most basic physics textbook.
Of course, they didn't have 3D printers to make solderless mounts, and the equipment was much worse(I'd imagine they probably still had analog oscilloscopes lying around!).
But then again, I was once asked by a friend who was about to graduate to come help with a college project. I know absolutely nothing about any of the math involved, I was just there to make some sensor data go on a WiFi network. We got everything done in a day, after they were fighting for weeks.
I think college just only teaches you the hard stuff, and then leaves you to figure out easy things like "Resistors have a power rating that isn't infinite" by yourself. Seems pretty reasonable given the fact college education people make 20 to 100 times more than me!
Re: Electron band structure in germanium, my ass (2000)
#84Earlier quoted context omitted.
Yeah I don't quite understand how the physics curriculum is set. There is more and more physics discovered over time and yet the time you get to study remains the same. 4 years is not enough time to learn the math and physics you need to do anything real, not counting the other important stuff you need to do (like English comp and partying and getting your heart broken).
Physics course is set to do two things (1) 'to teach you to think like a physicist' as my professor was fond of saying to us. No one is going to be able to learn all of the subjects knowledge in 4 years, let alone a complex and rigorous field like physics. (2) to give you a core foundation of understanding on which all other physics is built upon. By teaching the core subjects and lessons of physics, you can get a pr…
Thanks for the thoughtful response. I think maybe my objection to MY curriculum was being handed a lot of mathematical tools which I didn't need, and so it was impossible for me to "slot them in" to my toolbox. Most named solutions to differential equations were just like...why? (e.g. Bessel functions, or Green's function or...). I think it's a failure of pedagogy - I personally think you should give students the problem before giving them the solution. But the physics curriculum seems to want to give you solutions first and then tell you how you can use them. My brain doesn't work that way; tools fulfill a need. It would be like teaching a carpenter all the ins and outs of every tool in the shop, without ever building anything. How is the student supposed to organize that knowledge? Alphabetically?
I suspect that, just like how algorithms rarely pop up in software practice, so too do these kinds of tools pop up in physics practice, and when they do you probably get that same happy jolt of "Hey I finally get to apply this knowledge!" And that happens about once every 2 years.
Re: Electron band structure in germanium, my ass (2000)
#85Earlier quoted context omitted.
I was 3rd semester into theoretical math in 1999. Got a job on a side as a tech support. Then realised I am earning more in an entry level tech job than I can ever hope to earn in math. Did my 2 + 2 and went tech with no hesitation.
Applied math major here. It's practically CS anyway!
Well... I was in theoretical math (also not in US). We would be sometimes told by our profs that there is math and then there is this something that is being taught to everybody else, applied math included.
Applied math is essentially just learning the formulas to be able to solve real life problems. Not saying it is not useful. It is just something completely different from actually doing math research.
It is kind a like a difference between being a theoretical physicist and a mechanical engineer.
Re: Electron band structure in germanium, my ass (2000)
#86Exactly my experience back in the days doing the mandatory "advanced experimental physics laboratory semester" where you had to do like 14 vastly different experiment of the caliber described in that post in the course of one semester on old equipment that would break during the experiment, with less than motivated PhD students or post grads as teachers. Of the 14 experiments only two worked and we got the expected r…
Wow! I'm less than a year from applying to grad programs and all of my undergrad research experience is in very similar things. Theoretical is my jam. Did you do a PhD? If so do you now believe it was worth it?
In total, yes it was. Working for some years in a field, having the time afforded to emerse yourself into a subject and deeply think about it, calculating yourself into frustrating dead ends and also
into successes, writing papers, going to conferences presenting your results, have scientific exchanges with peers, write applications for research grants, sit in committees, work as a referee for scientific journals, teaching students, then writing a coherent and compelling thesis and finally defending it against & having a scientific discussion on eye-to-eye level with your supervisors will shape your character... a lot.
You might wanna skip that postdoc thing though if you know you don't wanna stay in academia (and trust me, you don't).
Re: Electron band structure in germanium, my ass (2000)
#87As an odd coincidence, I did the same experiment on a shoestring budget with substandard equipment also. I too used a fancy computer algorithm to get a best fit. Except that I managed to get four significant decimal places in the result — an improvement over the (also outdated) textbook. The author of the angry rant had a life-defining experience of overwhelming frustration. The same scenario resulted in a positive l…
Talking of a shoestring budget, sometimes it's a good thing. I actually learned more useful things about EE by fixing broken test gear than doing an undergraduate course. The course was so heavily theoretical that when it came to actually building prototypes, nothing worked and no one knew why, not even the lab techs. So I spent most of the time going round helping fixing people's limping final year projects. Life is…
Agree with this. I had to make my own equipment everywhere I went. The people I met later in my career who went to nice schools, with illustrious research experience had no idea what they were doing. Okay that's an exaggeration. But, when they entered industry they trusted every black box and rationalized every bizarre thing they saw as if their results depended entirely on their domain of interest.
Negative concentrations no problem! That must mean the machine is tracking the previous known value and this is the difference! Oh my oh my... The things I've seen the highly/expensively educated get paid lots of money to do, present, and be rewarded for in regulated industries....
Re: Electron band structure in germanium, my ass (2000)
#88This gives me fond memories.
I was not too recently ranting to some poor captive audience about the things which should and should not be labs, and how the topics existed on a scale of "doing science for primitives and stepping back into your time machine having advanced science by millennia" and "I swear everything related to this might as well be somewhere between voodoo and 1920s psychology." My ire was directed at calorimetry. They saddle high school students with calorimetry experiments, when really, as a field of measurement, unless you've got some great equipment and an amazing understanding of the possible hidden inputs, the error bars on your standard calorimetry experiment could accommodate a battleship doing a handbrake turn. At a high school level, calorimetry should be restricted to samples of ammonium nitrate dissolving in water and perhaps thermite, with checkboxes to indicate "got hot" or "got cold."
This is a similarly fraught deal and a cruel joke to play on an undergrad. Poor quality crystals, no explanation of appropriate solder, temperature control is non-existent. It's crap like this that turns people off of science. I have a physics degree and spent a lot of time tutoring; my big takeaway is that there exists a cabal of lizard people attempting to retard the technological advancements of humanity through a variety of gambits such as "social media," but that their biggest payoff has to be "labs."
And then, as a kind of extra special grift, are the kits. These are end-of-budget-year purchases which collect dust until someone gets the bright idea to actually hurl one of these beasts at the students. We received some kit involving fiber optics that was beyond terrible. I ended up tearing it apart and, with a DAQ and an XY plotter, created the world's slowest scanner. One thousand dpi, which isn't bad for 1992. The kit itself had pre-built experiments which seemed designed for little but frustration.
Even chemistry labs have better yields than this sort of thing. It's disheartening and students take this more personally than you might imagine.