Finite square well. Setting up the problem

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

[@10seabird]

Fantastic lectures. I had studied QM before but this presentation makes it so comprehensible

[@girishtripathy3354]

My left ear understood better than my right ear. Thanks prof

[@feelthedarkmusic7691]

Haha true 😂

[@girishtripathy3354]

@@MsMyrule ikr

[@GuruCharanGupta]

Hi! around @7:48 the subtitle says "and real exponential solutions depend on the sines" 'sines' should be 'signs'
@15:21 it says "know the sine" but sine -> sign
@22:29 it says "8x psi plane" it should be "eta-xi plane"

[@mitocw]

Thanks for the feedback! The subtitles have been updated. :)

[@silvadexter3222]

very clear !!!! ty for lecturing

[@mwangushyafrancis8383]

i greatly appreciate the presentation. i like it

[@loveforkitten2721]

You are really wonderful Sir. 😊😊😊😊😊😊😊😊😊😊

[@keshavmittal1077]

sir, what is the meaning of energy is negative?

[@cafe-tomate]

Waw that was a blast!

[@aartikhemnani3245]

ok i think some mistakes are there we can t ignore the negative signs because wave function changes ..

[@jerrydong8224]

Was searching up the finite curve song and stumbled upon this

[@aartikhemnani3245]

at 19:51 the kappa square + k square = some quantity , But left hand side is unit less but right hand side have some units how it is possible

[@BL1zZ4Rth]

They are all unit-free.
[ V0 ] = [ E ] = [ M L^2 T^-2 ]
[ hbar ] = [ E T ] = [ M L^2 T^-1 ]
[ m ] = [ M ]
[ a ] = [ L ]
k^2 = (2m) (hbar^-2) (V0 - |E|) => [ k^2 ] = [ (M) (E^-2 T^-2) (E)] = [ (M) (E^-1) T^-2 ] = [ M (M^-1 L^-2 T^2) T^-2 ] = [ L^-2 ] =>
=> [ η ] = [ ka ] = [ (L^-2)^(1/2) L ] = [ 1 ] thus unitless ,same with η^2 and we get the same result for κ (kappa) and by extension ξ and ξ^2, since the only difference between k and κ(kappa) is the replacement of the term (V0 - |E|) with |E| which we already know have the same units.
Now using that [ k^2 ] = [ L^-2 ] ,from the end of my first line of calculation we get:
z0^2 = (2m hbar^-2 V0) (a^2) => [ z0^2 ] = [ k^2 a^2 ] = [ L^-2 L^2 ] = [ 1 ] and thus is also unitless.

[@amirkhedri4562]

I have a question sir. In the case where |x|

[@igrib5852]

"You'd better do something about that cough"

[@ismahanemansouri9268]

Awesome thanks prof 😅 I am watching from Algeria I am a theoretical physicist and qm is crucial for us , or for all modern physics in general 😅

[@aimalkhan3229]

Sir what is the difference between particle in potential well and particle in a box?

[@res0nanc320]

The 'box' is a specific potential well.

[@vishnuakundi4766]

The box is 3-dimensional and so you will have partial derivates wrt the 3 coordinates of position (instead of just d/dx)

[@adosar7261]

Does any force exist in this potential well ? Both inside and outside the well the derivative of potential energy with respect to position is 0 therefore zero force. So what is the point to have 2 different potentials ?

[@zphuo]

Why k and kappa need unit-free??

[@michaelbenisty2116]

ZiPan Huo

[@Leonugent2012]

If you’re able to learn quantum mechanics you can learn it here

[@srivishnudasu1694]

14:06 if we are trying to find energy eigenstates , then they are supposed to be orthonormal anyways. why try to normalize at all?

[@shannonramirezslater4909]

great lecture. Whoever that was coughing like a person on their deathbed, take some cough drops man. That was so distracting

[@TonalWorks]

Or even better would be to stay at home, and so preventing the whole lecture hall from getting infected. Annoying and also inconsiderate

[@diags_1109]

@@TonalWorks you think that was annoying there is someone in my one lecture that constantly snorts his snot, like the snoring noise, during the first test they were going at it every like 20 or maybe less seconds for an hour and twenty minutes

[@javierortiz2128]

My professor did her post-doc at MIT and she cannot teach quantum mechanics at all. I had to go to the source to find a better instructor xD

[@peterpalumbo3644]

Can you do something about the noise from the audience. It is very hard to listen to the instructor with all the background noise.

[@STKeTcH]

I'm so glad I didn't go to MIT

[@pankajchaurasia4022]

not good ,could have been more understandable

[@HumbertLaxness]

why is it always the Indian complaining, i have seen your quality of lectures on TH-cam lol, completely incomprehensible