Lecture 12: The Dirac Well and Scattering off the Finite Step

MIT 8.04 Quantum Physics I, Spring 2013
Instructor: Allan Adams

In this lecture, Prof. Adams discusses the time evolution of Gaussian wave packets both in free space and across potential steps.

License: Creative Commons BY-NC-SA

[sonarbangla]

Enjoyed this lecture, the most detailed analysis of a wave with classical and quantum effect and also for standing wave. Simply great. I wish I understood it.

[ignaciomartinalliati]

3:47 "How surfaces bless you how surfaces reflect"

[atithi]

(25:18)I have tried to take the norm of the wave function but i am not getting a 2 in the denominator of the time-related factor. Is P(x, t) correctly written. Its not matching with mine

[davidhand]

Now that we are done explaining how the wavefunction behaves when bound to defined space, here's why wavefunctions cannot be bound to a defined space.

[sashankkrishna]

Thank you for the great lecture!
That said, 2:52 Caption corks -> quarks

[arkyachatterjee]

11:26 Why is the the minimum uncertainty wave packet for a free particle the gaussian? Also, what uncertainty is being talked about, is it the spatial uncertainty?

[pavlooliynyk]

Does anybody know and could explain why A=1 at 01:10:52? Thanks.

UPD. A typo was made, there should be A.(look up 13 lecture)

[HT-rqpi]

At 24:40, I am not getting the time dependent wave function that he is. I think he continued using that extra factor of 2 in the denominator of the power of the exponential which was a mistake that was pointed out earlier.

I'm probably wrong though, so can anyone let me know where I could've went wrong when taking the square of the modulus of the wavefunction such that I would end up without that factor of 2 next to the 'm' everywhere in the probability density function?

[volcanic]

How can we solve the system at 1:10:00 if there are 3 coefficients and 2 equations?

[peterpalumbo]

RE time mark 30./34 bell curve, you seem to be talking about the big bang and inflation incremental to infinity being a function of probability.

[datatraveller]

What was the joke at 55:53, about the tunneling barrier? I don't seem to get it... :/

[TheViscweaver]

@ 42:50 phase velocity= ω/k. How can group velocity be= ẟω/ẟk? Logically group velocity should be= ẟ(expected value of x)/ẟt. I tried calculating with Matlab but got an intractable expression. Please comment.

[hardikrajpal]

Honestly, Mr. Gopal Dixit, I would have very much preferred you recommending this to me yourself.

[ikarienator]

When was the minimum uncertainty wave function at 11:59 mentioned before?

[physicsperadox]

At 17.57 you wrote the solution of that curl psi as. Root a over 4th root pai e raised to something, how u get that pls explain

[peterpine]

Anyone has solution for challenge at 29:25?

[anugrahmathewprasad]

his office must be flooded during office hours

[KAG]

No one has commented on the fact this entire lecture was done in socks.

[prathamlokhande]

I don't understand a single thing here bt I can watch him whole day, lol !

[renelfcr]

Good day!


What thats program used for simulation plot to behavior the wave function and the energy and the probabilities in this class?
I'm brasilian guy, so sorry for the english errors within sentences.
Thanks!