Great lecture (series), but he seems to call phase velocity group velocity?! Each contributing 'plane wave' with PHASE velocity k is one component of the overall wave packet that moves with GROUP velocity k0.
In a previous lecture, he calculated that the phase velocity would be equal to half the velocity of the particle. This, of course, would not make any sense. Hence the use of group velocity which is d(omega)/dk. It is easy to check that it is equal to the velocity of the particle since d(omega)/dk = dE/dp = d/dp(p^2/2m) = p/m = v.
Kay Zero I believe that it is because we only care about the maximum value of k-ko. Anything less that deltaK would be even smaller than 1, and we can ignore it.
Great teacher ....! A rarity nowadays !
why k minus k not equals uncertinity in k?
Amazing lecture.
What happened to the 1/2 at 6:58
Michael Lewis it wouldn’t matter anyway since you want the value to be really small, and multiplying it by 1/2 would just make it even smaller
Thanks ❤️🤍
Great lecture (series), but he seems to call phase velocity group velocity?! Each contributing 'plane wave' with PHASE velocity k is one component of the overall wave packet that moves with GROUP velocity k0.
In a previous lecture, he calculated that the phase velocity would be equal to half the velocity of the particle. This, of course, would not make any sense. Hence the use of group velocity which is d(omega)/dk. It is easy to check that it is equal to the velocity of the particle since d(omega)/dk = dE/dp = d/dp(p^2/2m) = p/m = v.
why k minus k not equals uncertinity in k?
Kay Zero I believe that it is because we only care about the maximum value of k-ko. Anything less that deltaK would be even smaller than 1, and we can ignore it.
I don't know, Kay. Or is it k? 7:37
I am getting 10^-20 seconds as an answer in the last question. Idk if I am wrong I did everything corrct
No, the professor is right. m_e / h_bar * 10^(-20) m^2 is about 8.64 * 10^(-17) s, which he approximated as 10^(-16) s