Free particle wave packets and stationary states

The construction of wave packets from infinite traveling wave stationary states is described, including a qualitative derivation of Fourier transforms and a discussion of wave crest velocity (phase velocity) vs wave packet velocity (group velocity). (This lecture is part of a series for a course based on Griffiths' Introduction to Quantum Mechanics. The Full playlist is at ruclips.net/user/playlist?list=...)

[@xXxBladeStormxXx]

Absolutely beautiful exposition of Group and Phase velocity! Those slanted lines were great!

[@Gismho]

Yet another superb video. This is a really interesting series, very well explained and described. Thank you professor once again.

[@timetraveller1237]

excellent work about group velocity and phase velocity understood it at right the last animation thanks so much

[@ishkool8664]

Check your understanding:
1) False: for k

[@OmnipotentO]

I believe I heard it from the Leonard Suskind lectures about how classical physics is what emerges when you take the collective averages into consideration. and you kind of demonstrated that here with the k bar at 30:30. Amazing.

[@ramasatya6317]

Thank you very much!! beautifully explained.

[@xXxBladeStormxXx]

Did I just watch a twisted derivation of the Fourier Transform? :O

[@shavuklia7731]

Twisted but effective!

[@nickolasconnor3661]

i guess I am kinda off topic but do anyone know a good site to stream newly released series online ?

[@brendanxzavier3649]

@Nickolas Connor try FlixZone. You can find it by googling :)

[@atticuskoch2965]

@@brendanxzavier3649 you arent fooling anyone

[@obaidurrehman2464]

Thanks ...
I really liked the introduction of wave packet ....

[@solsticetwo3476]

Great course! Thanks a lot man

[@HT-rq5pi]

what is the answer to the "check your understanding" qst. Its pretty hard to check ones understanding not knowing the answer.

[@philandros3195]

Ye, that's the one short coming of these videos.. he didn't upload the answers anywhere accessible to people.

[@manishsingh-vk8if]

May be he doesnt know the answers.

[@shahadas907]

Many thanks! it helps me a lot :D

[@assemafanah8622]

thanx a lot :)

[@princeistalri7944]

Why did you assume k_1 is approximately equal to k_2 at the end there? What would happen if you assumed the difference between k_1 and k_2 is arbitrary?

[@Kraflyn]

Hi. If k1 and k2 are far apart, the calculations are the same, the result is the same, but the animation is more "fuzzy", the animation wouldn't be so "neat". Cheers :D

[@hershyfishman2929]

28:24 that should have a t (as corrected later at 30:12)

[@the-fantabulous-g]

18:25 Check your understanding: I simplified my answer down to (1/(2*sqrt(pi * a))) * (ike^(ika) - ike^(-ika)).
35:45 Check your understanding: All false, but that's a Hail Mary from me. I have no idea about this part, I'll appreciate anyone who can explain (for me and those who come after).
Let me know if anyone differs in answers, thanks!

[@the-fantabulous-g]

For 18:25 we can probably apply a trig identity. It looks possible at least.

[@pixelberrychoicespodcast5861]

I got something similar to that the first one I mean phi k

[@stopwatcher8930]

The first one looks more like a derivative. When you integrate e^-ikx you have to pull out -ik out of the 1 in front of the e. So basically (-1/ik)*e^-ikx.

[@titimilidbz]

21:54 Quantum Mechanics in a nutshell

[@huanghan1911]

There is a mistake: Integrate(exp(ikx) exp(-Ik'x))=2 Pi delta(k-k'), not just delta(k-k')

[@axelarnone155]

Could you point out where in the video?

[@huanghan1911]

Axel Arnone 12：22

[@manishsingh-vk8if]

Seriously this person is very confusing.