== Past news of persistent value == {{{#!wiki arcnews * If you like to submit your solutions to some or all problems of Homework 8, for extra credit, then the due date is: '''5 PM Dec 13 (Friday), if you plan to hand in your homework in person''', or 9 PM Dec 15 (Sunday), if you plan to submit your work by email or by forum posting (forum discussion is very much encouraged, as always).—~-''<>''-~ * The solutions to the final exam had been posted. Please download them from [[Homework+]] (and read them at your leisure during the holiday break).—~-''<>''-~ * There are <> that relate to the final exam. Please let me know if you have difficulty accessing them.—~-''<>''-~ * There are no news items to post this morning—just doing a virtual “mic check” here. I can almost feel the heat with which all students are working very intently on the exam! Be confident (but don't be over-confident), and get those problems done—'''You can do it!'''—~-''<>''-~ * A paragraph is added to [[Lecture+#Lecture_Notes|LN 7 (page 8, just before Section 7.5)]]. This may be important for you to consider in doing homework 4.2.—~-''<>''-~ * In doing homework 4.4, you would need to use the so-called ''(electric) dipole selection rule'' for the transition: $$ \Delta j = 0, \pm 1 \text{ (but no }j = 0 \rightarrow 0 \text{ transition)},\; \Delta l = \pm 1,\; \Delta m_l = 0, \pm 1.$$ We will be able to derive the last two selection rules later on (or you might be able to prove them already!), but for the first one you will have to wait until you take the graduate level quantum mechanics.—~-''<>''-~ * I guess I will see many of you tomorrow during my office hours ('''noon-2PM'''). In addition, please feel free to ask your questions on the forum or by email. '''Good (= sincere) discussions will really protect you in my course''', since (1) you are a learner—I/you/anybody should never expect you be a knower already (although you could be close or already there)—and (2) your willingness to learn will make people (esp., me) respect you very much.—~-''<>''-~ * Office hours: Monday <>, Thursday, Friday, 1-2 PM, or OBA. (Syllabus updated.)—~-''<>''-~ * There are some discussions of homework problems in the <>. Check them out!—~-''<>''-~ * '''~+Welcome back, students!+~''' }}} == Past news of purely archival value == {{{#!wiki oldnews * One addition and one correction to the exam (both of them marked <> in the <>.) (1) “spatial” added in Prob 5. (2) “to” → “of” in line 3 of Prob 6.—~-''<>''-~ * The final exam is posted now. <>. Watch this space for any news about the exam.—~-''<>''-~ * Homework 4 is due 5 PM, Wednesday, Oct. 30.—~-''<>''-~ * For problem 4 of homework 2, it would be sufficient to prove that $\langle n^{(0)} | {\underline n}^{(j+1)} \rangle = 0$ for any $j = 0, 1, 2, ...$. The ket $| {\underline n}^{(j+1)} \rangle$ is defined in <>. In the same image, you can find other information. For example, four completely equivalent statements, important for this problem, are noted in the green rectangle. The equivalence of these four statements can be proven based on Eqs. 3.19 and 3.20, alone. This is kind of demonstrated in this image, and you are ''not'' required to demonstrate it yourself. '''Just prove that $\langle n^{(0)} | {\underline n}^{(j+1)} \rangle = 0$ for any $j = 0, 1, 2, ...$ (using the proof by induction).'''—~-''<>''-~ }}}