# [PHYS G4021] Quantum Mechanics I

- Departments: Physics
- Professors: Philip Kim, Andrew Millis, Alfred Mueller, and Erick Weinberg

Avoid. Unless you're a physics major, in which case you'll have to take this class and in all likelihood Prof. Weinberg will be teaching it, which makes your life doubly sad. Quantum mechanics is difficult, but where it could've been made interesting, Prof. Weinberg fails to do so on every count. He drones on in class, and places random equations on the board that he expects you to remember from last time (you won't), and gives little or no context for it. For the most part, he covers what's in the textbook, but not always, which can be frustrating since I found most of lectures impenetrable. First part of the semester leading up to the first midterm was alrightâ€”basically a recap of 2601 and covers the Schrodinger equation in 1 dimension with various potentials. Then, the class moves into grey areas when Prof. Weinberg spends a good chunk of time reviewing linear algebra in the most unenlightening way possible. This is where he lost my attention. The subsequent part of the course involved recasting quantum theory in the language of linear algebra, so I found myself playing catchup every lecture. One thing though, Prof. Weinberg curves pretty generously, and the class tends to have a HUGE spread in raw scores, so good or bad depending on who you are.

#### Workload:

Weekly problem sets (10%), 2 midterms (25%+25%), 1 final (40%).

I won't speak for others (I hear through the grapevine that some others liked the class less) but here's my impression:

Professor Weinberg loves the subject and is an enthusiastic teacher. He follows the textbook (Griffiths, Introduction to Quantum Mechanics) pretty closely so if you feel like it you can read along during the semester. Sometimes he'll deviate from Griffiths sequencing, but he usually announces this a lecture ahead of time.

If you're a real physics whiz, you probably don't have to come to class but my general observation from sitting in the front row all semester was that the top grades seemed to be clustered there -- Weinberg does add value with his lectures, unlike some physics profs. This semester, probably owing to the way the classroom was laid out, the class was pretty intimate. People would ask questions mid-lecture without raising their hands and would interrupt derivations to point out mistakes or ask about a technical point, and Professor Weinberg just rolled with it. I had fun with that, though I can understand if others found it distracting.

In general, the class's material isn't too difficult, but it gets harder as you go on. For the second month you should make sure you know your linear algebra, and for the final month you have to make sure you've got vector calculus down cold. On the hardest homework problems I found myself resorting to the solutions manual for hints (it's is available online if you look hard enough) but be warned: the homework isn't worth enough to be worth cheating on, and is at the same time crucial to picking up certain concepts that Weinberg uses the homework to teach that will appear on the far more valuable exams.

Up to the first midterm is stuff you'll probably already know, i.e. Schrodinger, infinite square well, harmonic oscillator, and a bit of knew stuff, i.e. delta-function well, and the free particle. The first midterm was very straightforward; four problems you could do if you had paid attention in class. I lost all my points on a dropped negative. The median was a 50 but it was pretty bimodal. A bunch of people clustered above 90 and a bunch clustered below 50.

The second midterm covers the matrix interpretation of quantum mechanics and all it implies, including a bit more on the free particle and delta well as well as the uncertainty principle and observables as eigenvalues. This midterm was a lot harder -- two fairly easy problems, two problems that were impossible if you didn't spot the trick (though in fairness the trick for each had fairly prominently figured on the homework) -- had a much tighter distribution, though the median was 50 again.

The last month of the class is quantum mechanics in 3 dimensions. The hydrogen atom, angular momentum, spin, etc. At this point (almost literally the day after the second midterm) I lost track of the class. I did vector calc as a freshman (senior now) and linear algebra in high school and that came back to bite me in the ass. I'm starting to get caught up now, but it wasn't fun. I'd say how I did on the final, but I'm writing this before it to avoid being biased by how I do on that.

#### Workload:

Weekly homework, 10% of the grade. Two midterms, each 25%. Final worth 40%. He said that the median grade was the A- cutoff last semester. I'm on track to be a bit north of the median, but not a lot.

Quantum Mechanics is a tough class. No getting around that. Unless you are one of the handful of people ruining the curve because you have taken Brian Greene's equivalent course already or are enrolled in both. Despite the large amount of variation in background, the class was my favorite this semester. The material is really interesting and Prof. Mueller is not bad lecturer.

Pros

--Mueller is really nice

--Questions are answered graciously

--The material is interesting

Cons

--The book, Gasiorowicz, is not great. The problems are impossible, there are no examples, and the explanations are brief.

--Because of the variety of backgrounds of the students in the class, the curve hurts

--Prof. Mueller goes through the material very quickly.

Overall, a good class.

#### Workload:

Homework doesn't count for the grade and the exams do not resemble the problem sets in the slightest. However, if you do the homework, you will get a lot more out of the class.

I am shocked at some of the reviews that Professor Kim got in the last few years, and I can only chock it up to a very steep learning curve in his teaching style. Kim is among the best teachers in the physics department, and you will find very few people in the Quantum Mechanics class who disagree. His lectures are integrated well (heh heh) with the textbook so that they supplement and reinforce each other, and I always leave class with a better understanding of the material. There is a lot of material to speed through, but he is very good at boiling down concepts, explaining derivations and getting excited when something cool happens (like the Hydrogen atom). Quantum was definitely my favorite class of the semester.

Problem sets are long and difficult - make sure to start at least 3 days in advance - but they build knowledge of physics and useful problem-solving techniques, so you will learn a lot from the problem sets. Exams are pretty fair: 3 or 4 problems with 1-3 parts, and an average around 60. The curve is nice.

Summary: ignore the 1400 comments (a good rule in general) - Kim should have a gold nugget. Be prepared to learn some serious physics.

#### Workload:

10 weekly problem sets, 6-20 hours long (no kidding!), one midterm, cumulative final

Professor Kim was the best physics professor I've had here. He respected the students, as well as the subject matter and did an excellent job filling in where griffith's ran short. He ran his own recitation section which turned into a third lecture because there was so much he wanted to teach us. Depending on the amount of math involved, the hw's took 5 to 40hrs so get mathematica or at least use the integrator online. The first midterm was extremely long, but the final was ok with the second semester being the opposite.

He's a sweet guy that will actually recognize and say hi to you, and is also someone who really knows his physics and teaches it well. This was his second year teaching it and he seemed to have a very clear lesson plan for each class that left plenty of time for the inevitable questions.

Watch out for his TA's though, they have no idea how to run a recitation or help you with your hw.

#### Workload:

Problem set per week (usually about 15hrs, less if you use mathematica), one midterm and one final per semester. This was the most work I've done for any physics class up until this point.

Professor Kim makes this class a pretty painless experience. The majority of his lectures are drawn directly from the textbook (Griffiths "Introduction to Quantum Mechanics") and he works through the material at a fair pace, so it's not very hard to keep on top of everything. It was his first time teaching QM, but I think that he did a good job.

The homework problems were mainly drawn from the textbook. Overall, the difficulty was typical for a physics class, although some problems were algebraic nightmares, involving endless swarms of integrals. I'd definitely recommend using mathematica to do at least some of the computations; it'll save you a lot of time.

The exams basically regurgitated the material covered with homework problems - if you fully understand the homework, the tests will definitely be doable. The averages generally seemed to be in the 60s or so. I don't know how the grades were ultimately curved, but everyone I spoke to seemed satisfied with their final grade.

It's also worthwhile to point out that the homework problems in the second half of the second semester seemed a bit harder than the earlier ones. I also felt the 4022 final was harder than the earlier three exams. It may have been the specific material that we were covering, but I think that Prof. Kim may have been intentionally making everything harder - this may carry over into Fall 06. But everything's curved ANYWAY, so who cares.

Prof. Kim is very approachable and helpful and the class should only get better as he gets more experience teaching it. At times, the mathematical rigor of the class is questionable (as made evident by the entertaining smart-ass questions that were occassionally asked), but that's expected for an introductory class that covers a wide range of material. Overall, I'd call it a very good experience.

#### Workload:

Weekly problem sets of varying difficulty. A midterm and final modelled closely after the homework. The total amount of work/studying required is about average for a physics class.

Prof. Millis is one of the worst profs that I have ever had. In class he frequently makes mistakes on the board. I couldn't even use my notes to study for the final exam because they were so full of mistakes! He also has an awful habit of erasing equations immediately after writing them. You would think that the obvious distress of the class when he does this would be enough to make him stop, but he keeps right on doing it. He also has a habit of using notation different from the book which is confusing. The homeworks are incredibly long, but don't try to start on them too early because half the time they are full of mistakes that he corrects by email. Each homework includes an incredibly worthless Mathematica section that takes hours and doesn't help you learn the material at all. If you manage to understand the material on the homeworks the tests are hard but not impossible. If you plan to take this class start looking into alternate text books early because Griffiths is horrible.

#### Workload:

Insanely long homework assignments (kiss your other classes goodbye), with idiotic mathematica sections. One reasonable midterm and a final.

I was very frustrated by this class. Granted, it's hard stuff to learn (much less do problems on), but Millis did nothing to facilitate it whatsoever. He made several mistakes which he spent far too long trying to recover from, ended up wasting class time, and would even come to the next class with the real derivation, spending even more time belaboring an example I could follow ten times more clearly in the textbook. Also, he had a terrible habit of erasing entire equations immediately after writing them, replacing them with the next step and making it impossible to copy anything down, especially when you're dealing with spherical coordinate Schrodinger Equations with five greek letters and partial derivatives all over the place . He called it "algebra by erasure" but I call it terrible teaching. I came out of the class with such a remedial understanding of quantum mechanics that I was prepared to take it again next semester, but guess what--he's teaching it. If you already know a lot of the material and are prepared for an awkwardly-paced, often confusing coverage just to strengthen your understanding, I suppose he wouldn't be so bad, but I honestly could not deal with him and do not recommend you find out for yourself, because you might not realize his faults until it's too late.

#### Workload:

Relatively difficult weekly problem sets that don't always relate to the material covered in class or the textbook. Also, he has no flexibility if you don't finish it on time. The exams weren't so bad after the curve, and I definitely deserved worse than a B- (what I got), but overall this class is plain hard.

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