nvm found the relevant section in the book

For an electromagnetic wave which propagates in some arbitrary direction and it's true that $k_z=\sqrt{k^2 - k_x^2 -k_y^2}$ is imaginary, it means that alongside the z axis, the wave doesn't propagate. Does this mean that we can have components of an electric field that propagate and can be mathematically represented with plane waves, and components that are evanescent waves?

wait does that work lol

that's so cool :P

seems like yes? @imbaf

I'm genuinely surprised Sakurai doesn't bother to derive the Dyson series

Seems bizarre since it's got an honestly cool derivation in other books

Well this technically is a derivation, but it feels like a speedrun

Dyson series any%

what book is that one

the picture? Sakurai

tbh sakurai started out really good but has been kinda declining in quality lately

guess he got tired of deriving a lot of things and just said to look at other books

ohh I see what u mean

wish he didn't point to Townsend though

I feel like the point of a textbook is to guide the reader and deriving results plays a pretty big role lol

I'd say it's essential. If you're not going to bother doing that then don't write a book. The exception is if the derivation is just tedious but not difficult, or if it's just a copy/paste of a previous derivation with slight modifications.

well there are sections in this book that just really drag on because he goes into every detail on the derivation

which gets surprisingly boring

but then conversely there are sections where he just drops things out of thin air and says to read other books for the derivation

it's pretty much one extreme or the other

I don't mind it if the author explains the gist of the result & how it's derived. Schroeder is so laid back in that way which I appreciate. Not that the derivations are actually that hard (I guess they can be, depending on how rigorous you want to be)

but stat mech/thermo is a lot easier to comprehend since it's not as abstract as QM

shrug

well it kind of depends

schroeder made statmech very intuitive for me

but then my graduate textbook made it feel incredibly difficult

so I've had a much easier time with graduate QM

it really comes down to whether you get a decent book at the end of the day. which is up to luck given that the prof chooses them

@SirCumference in what way

@Obliv Sakurai honestly does a very good job connecting QM to (higher level) classical mechanics

yeah I guess it depends on the book and course. Any subject can get absurdly difficult :P

at the end of the day it almost feels like a modification of familiar things rather than a completely new topic

what did u use for undergrad QM

Townsend (garbage)

@SirCumference yeah that's ideally how it is.

that book is ass. just dropped the topic out of thin air and made every result seem arbitrary

sakurai is far better on the whole

ok well I hope we don't use it in the fall for my class lol

I read some Shankar too back then and it was a much better introduction

also heard good things about Griffiths QM

tbh anything other than Townsend is probably good

As someone who had tried reading both Griffiths and Shankar, I'd say Griffiths gives more intuition, and Shankar is more mathematically rigorous.

Though, I cannot say much when they were mere tries.

I don't really like griffiths for EM (not that I read it all the way through)

but maybe QM is better

@Obliv that's surprising, it's probably my all time favorite textbook

made every section feel intuitive

What about CM? I don't think there is an agreement about its textbooks.

@DannyuNDos as far as undergrad, I had Taylor which was mostly top notch (though its section on rotation is really not good)

It just feels really long and drawn out lol adhd kicking in

CM I had my professors lecture slides

:D

for graduate I didn't have any book since my prof just gave out his notes instead

@Obliv same here lol

I've supposed to be studying for two tests I have this tuesday

same lmao

but i keep getting distracted because perturbation theory is very boring

thermo in the morning then em

I mean, I'm frustrated being taught Newtonian mechanics over and over again. Just give me Lagrangian and Hamiltonian already.

@DannyuNDos Taylor was my book for Lagrangian mechanics

though Hamiltonian mechanics is only a footnote in it, which is really stupid

I'm still in the fun explorative part of learning physics so I can't relate as much :P

I feel like schools should mandate teaching Hamiltonian mechanics before QM

so much of the topic becomes clearer when you've seen the classical analogs

@DannyuNDos typically from where I'm from you see it maybe once without calculus, twice with calculus and then lagrangian/hamiltonian mech lol

unless u get credit from high school for AP exam in which case u just see it once with calculus

Yeah. And the worst thing in my institute was, they taught elementary EM without teaching multivariate calculus. Now they regret that.

@DannyuNDos yeah, they did that for me too

was a nightmare

had no idea what all these crazy looking integrals and derivatives were

I basically got nothing out of my first EM class. thankfully my second one started from the beginning with Griffiths so I came out feeling much better at it

though they never went over circuitry in the second class, so my knowledge on that is empty at this point

anyways i need to get back to studying