Momentum operator, energy operator, and a differential equation

MIT 8.04 Quantum Physics I, Spring 2016
View the complete course: ocw.mit.edu/8-04S16
Instructor: Barton Zwiebach
License: Creative Commons BY-NC-SA
More information at ocw.mit.edu/terms
More courses at ocw.mit.edu

[@ricardocesargomes7274]

The best Lectures of Quantum Physics!

[@shadmanyakub1494]

Ricardo Césa what is the teachers name?

[@lexhuismans3604]

It is in the description: Barton Zwiebach

[@michaelcordova1803]

Barton Zwiebach es peruano.

[@rajinfootonchuriquen]

@@michaelcordova1803 al buscarlo pensé que iba a ser de esos latinos criados en EEUU, pero es nacido y criado en el Perú. Que bueno que hay gente que independiente de donde venga logré grandes cosas.

[@richardhall9815]

It's cool that they actually show the students in the front at the beginning of the video. I've been wondering for a while whether he was actually talking just in an empty room in front of a camera or if it was an actual lecture with students there the whole time.

[@VijayKumar-pk1sx]

Professor is so cool...he explains everything with patience and...best part is that he carries proof...MIT stands apart from the rest of universities around the world...I miss studying in this university ...buut any ways seems to have a substitute..love you MIT but you may not ....but i love you anyways:-)

[@schmetterling4477]

He teaches nothing that you can't get exactly the same way at any other university in a Western country. Physics undergrad education is pretty much the same all over the developed world. If there is a working restroom in the building, then this is what you get in QM101. Your problem is that you don't even have a working restroom. :-)

[@juliogodel]

Just marvellous.

[@RajeevSingh-ki8bc]

I want more lectures from that professor

[@ismailbaris7181]

Amazing. Thank you very much.

[@waibenglam756]

Excellent. Wished his lectures were available when I was I was an undergrad. p/s Professor Zweich does look a bit like Harrison Ford without his glasses on!

[@rahuldhungel]

Did he ever take that Voigt-Kampff test himself☺️😉?

[@ashokpillay6343]

Well explained!!!

[@vinodkancherla4504]

Walter Lewin, Barton Zwiebach, Leonard Susskind, R.Shankar can motivate students!!

[@rezokobaidze8501]

thanks a lot

[@Ajaysingh-fl1vf]

just wow sir

[@user-kb4wz1yq1g]

6:22 momentum operator

[@wagsman9999]

Awesome

[@oscaraguilar6906]

guapisimo

[@AirborneLRRP]

My only qualm is that Ehat operator is actually defined as ihbar d/dt. In this case, with no potential energy it in fact is equal to the energy operator. With potential total energy would not just equal kinetic, so the way we defined the energy would not be an eigenstate of the energy operator, which defeats the our purpose of the operator.

[@rajinfootonchuriquen]

Given the relation (operator -> observable). If you have a decomposition of the observable, its operator is also a decomposition of other operators. The potential occurs if you find a scalar field that satifies a gradient equation, so in a big sense, defining the energy operator as a composition of potential operator is more general that thinking of a composition of potential operator plus a potential operator.

[@ingeniouswild]

Yeah I reacted to this part as well, he says a couple of times that the p^2 is the "energy operator" but conceptually I think it helps to think of it in reverse - p^2 is just, to start with, the "p^2 operator" and the *physics* of the particle in this situation that you already have (E=p^2/m) tells you that this operator operating on the wavefunction should give the same result as the energy operator operating on the wavefunction that was previously defined.

[@surendrakverma555]

Very good 🙏🙏🙏🙏🙏🙏

[@anishgade4050]

Deriving Schrodinger's Equation by my own hand is the most exciting thing in the world

[@schmetterling4477]

Schroedinger's equation is unphysical, so you can't "derive" it from rational first principles. Not sure what you think you are doing, but it is certainly not a "derivation".

[@ladyalexandra2980]

Congratulations, not even Schrödunger could do it. He dreamt of it or so.

[@user-kb4wz1yq1g]

18:31 energy operator - 2nd derivative

[@romeovalentin5524]

At 14:10, it should be E*psi=p^2/(2*m) I think

[@mfoucault1984]

somebody told him just a moment later..

[@iwonakozlowska6134]

It's like a "heat equation" with an imaginary coefficient.

[@rajinfootonchuriquen]

Yeah. It should be called the Schrodinger's diffusion equation, but maybe "wave" is more catchy

[@cafe-tomate]

He is talking about the exponential but the wavefunction Ψ is the the integral of these exponentials times a function Φ
Note that Ψ is an eigenstate of the p operator (p hat) only if Φ peaks narrowly around a certain value (the eigenvalue being p of course)

[@vinodkancherla4504]

Love you, Professor!

[@kaushaljain5999]

12:15 to 12:24 What did you say at this time?

[@philos22]

Look at subtitles

[@theconstellation__]

But E=p^2/2*m is for non relativistic particles
What about photons

[@schmetterling4477]

Those need the real theory. This is just a toy theory for those who will never do serious physics.

[@rahilshaik1603]

you just use the relativistic formula, E^2 = p^2c^2 m^2c^4

[@joshramer7]

Truly, the Harrison Ford of physics!

[@Janlyuk91]

Ahahaha

[@rahuldhungel]

Did he ever take the test himself?😉

[@juanfa98]

Jefe

[@sumitbhoi0074]

Better than Wikipedia lol

[@faustogadani3075]

the pronunciation of De Broglie name is uncorrect. But the prof is ok

[@ManojKumar-cj7oj]

It's incorrect* not uncorrect

[@channeldoesnotexist]

Your comment is in a superposition of correct and uncorrect

[@zackarykutler5348]

I give my girlfriend my *De Br OG Ley Wavelengths* sometimes.