Please Stop Using Griffiths' ''Intro to QM''

1. Sep 28, 2008

qspeechc

Hello everyone.

I wanted to make this thread to asks lecturers to please stop using Grffith's book "Introduction to Quantum Mechanics" as the required text for undergraduate physics, and to warn students about it. Please read this, as I truly believe Griffiths' book is a rip-off, nevermind a bad book, and that there are far superior introductory QM books out there. Let me explain.

Firstly, there is the price. Over $100.00 is ridiculuous when there are many good introductory QM books that are roughly half the price: Shankar, Baym, Rojansky, Bransden & Joachain, Zettili,.. you get the idea. I will return to this topic later. Secondly, you don't get much book for your buck. Griffiths seems to want to explain everything with the least amount of words as possible. He states that the book does not cover enough material to make a full year course. I find this difficult to fathom considering the price and the size; surely he could have added more topics? Thirdly, most importantly, this book is a horrible pedagogical text. For this book one merely needs to know how to take partial derivatives. In other words, any one who has passed their first year could read this book. You may think this is fantastic, as it makes the book simpler to read, alas, it does not. For instance, Griffiths explanation of the seperation of variables technique is painful. The only reason I could follow his writing is because I had done partial differential equations prior to the course. Those who had not were confused by this. Griffiths does not even expect you to know linear algebra (it's all in the appendix) or to solve an ordinary differential equation-- he always supplies the answer and tells you to check that it is correct by substituting it back in the formula. Griffiths does not explain anything. At the very beginning of the book the Schrodinger equation is thrown at the student. Not much is said about it, what it means, the justification for it, how this departs from classical mechanics-- Griffiths does not say. As a result one does not know what they are doing or why. Isn't the reason we do physics is because we enjoy it? Griffiths does not motivate anything. He says ''Here's a situation that occurs in QM, here are the equations relevant to this situation, and mathematicians tell us that this is the answer'''. Read the book, it really is like this. This is very much a rubbish way to teach anything. Griffiths never even properly explains what the wave function is all about. When I look at this book this is what I see: here are a bunch of differential equations that occur in QM, and if you told a mathematician to solve them this is what you get as the solution. The book is horrendous. Griffiths exposition is terrible. Many pretty pictures are fine, but I want substance. He leaves out much theory that would make QM easier and more understandable. His organization is terrible. He introduces very little theory at first, and gradually introduces the theory throughout a few badly explained examples. What you get is an incoherent theory scattered throughout he chapter, and no overview of what you have done. Other books present general theory (and more theory) before the examples, which serve to illustrate the theory. After the examples more theory is given, and this is how it should be. QM is simpler with more maths, as Griffiths himself admits, but the only prerequisites for his book is taking partial derivatives. QM is much, much simpler if the author assumes the reader has knowledge of linear algebra, advanced calc, ODEs and some elementary PDEs. Students who do not have this math background SHOULD NOT BE STUDYING QM! Griffiths provides very few examples in each chapter, and leaves essential ideas and theorems to examples. There are no answers/solutions to the problems, and I have no qualm with this. Except, if you are going to require very fundamental ideas are left as problems, the student can get a totally wrong set of fundamental principles if left unchecked by not having the answer. Also, many of Griffith's questions are very vague, and one struggles to figure out what he is asking. Many of the questions are stupid mathematical arguments. Griffiths is inonsistent. He does not expect you to know integration by parts (he explains it in a footnote), but expects you to understand terms like "canonical substitution". At one point he defines the transmission coefficient as |F|^2/|A|^2, and then in a later problem he says "prove that in this instance the transmission cofficient is not simply |F|^2/|A|^2. This occurs in chapter two. He does define it this way, he uses the equality sign with three lines. This sort of inconsistency occurs throughout the text. If Griffiths had simply defined the transmission coefficient correctly at the start this would have been avoided. His theory is patchy and he does not give all the theory you need to solve the end of chapter problems, or even to understand QM correctly. I have more problems with the book, but at present they elude me. There are so many faults and short-commings I cannot recall them all at present. When I read the book again I will surely spot more. Please, please, I beg you, do not use Griffiths. Griffiths is for people who want to look cool posing with a book on QM. Two excellent books: Zettili and Bransden & Joachain are both far superior and$40 cheaper. I understand profs may think Griffiths is simpler since it requires less maths, but as I explained, this is part of what makes it a bad book. All the other good undergrad QM books use much more maths and are much better for understanding and technique; all-round much better books. Profs also like Griffiths since it has no solutions. Try, for one year, to use Zettili or Bransden & Joachain instead of Griffiths, or get yourself to use Griffiths and one of the other books, and judge for yourself. Bransden & Joachain cover much more material. Zettili has worked problems. Both give more theory, explain everything much better, and just have much more content. Zettili is at 650 pages and B & J over 700 (in the first edition). Griffiths books has roughly half as many words per page too; I know, I've counted. Even the paper Griffiths book is printed on is inferior. Please stop using Griffiths QM, this is a passionate plea from an undergrad. I truly believe Griffiths wrote this book to make money. There is very little content and substance to this book, especially for the price and compared to other undergrad QM books. A first year student could read the book there is so little mathematics. I believe he did this on purpose to entice ill-prepared over-zealous young students. Please stop using it.

Last edited: Sep 28, 2008
2. Sep 28, 2008

atyy

I've never used Griffiths except from a peek or two into a friend's book - his cats are cute, especially the one climbing the ladder

3. Sep 28, 2008

qspeechc

Yes! You've just reminded me: the largest image in the book is that of a cat climbing a ladder, pertaining to ladder operators. How does this help? He should have instead used the space to properly explain ladder operaters, and operators themselves for that matter.

4. Sep 28, 2008

will.c

Unless Baym has a quantum book other than this (http://search.barnesandnoble.com/bo...url=Lectures-on-Quantum-Mechanics/Gordon-Baym) it is ridiculous to suggest it as the course book for an undergraduate quantum class.

I think the problem is that you skipped the niche that Griffiths is trying to fill. It's like complaining about algebraic approaches to introductory physics, when you were done with the calculus sequence before you even got to college. If you've already mastered linear algebra, partial differential equations, etc. then take the graduate course - no worries. To suggest that the undergraduate course should be at exactly the level to which you've already reached, and that students without your background are undeserving of learning quantum mechanics, is rather elitist.

Finally, just because a book has a bigger breadth of material doesn't mean its better, pedagogically, or else we'd all take quantum out of Cohen-Tannoudji. If the cost of the book is off-putting, order the international edition.

5. Sep 28, 2008

qspeechc

Please compare either Zettili or Bransden & Joachain to Griffiths, and see the levels of mathematics used in them. Then tell me the typical undergrad cannot do QM from Zettili or Bransden & Joachain. You need to know no more calculus, ODEs and PDEs than you would for an undergrad EM course, and no more linear algebra than is contained in Griffiths QM book. Those books were written for undergrads by experienced teachers on the subject to undergrads. No deep or extensive use is made of those mathematical topics, but nevertheless they are used more, and to far greater advantage. Suggesting Baym was a mistake, but my point about there being many better books out there for the undergrad still holds.

Last edited: Sep 28, 2008
6. Sep 28, 2008

olgranpappy

In my opinion, Griffiths is a good introductory book. The presentation of the material is often simplified, but still clear and honest.