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--- classes:2009:fall:phys4101.001:lec_notes_0930 [2009/10/01 23:57] – yk
+++ classes:2009:fall:phys4101.001:lec_notes_0930 [2009/10/02 00:07] (current) – yk
@@ Line 9: / Line 9: @@
 **Main class wiki page: [[home]]**
-Please try to include the following
+//This note complemented my actual lecture with proper factors so that "~" becomes "=", and some parts that perhaps I was not clear (from your faces) were more clearly and completely explained.  Thank you for you the wonderful job.  Yuichi//
-  * main points understood, and expand them - what is your understanding of what the points were.
-    * expand these points by including many of the details the class discussed.
-  * main points which are not clear.  - describe what you have understood and what the remain questions surrounding the point(s).
-    * Other classmates can step in and clarify the points, and expand them.
-  * How the main points fit with the big picture of QM.  Or what is not clear about how today's points fit in in a big picture.
-  * wonderful tricks which were used in the lecture.
 === Main Points ===
@@ Line 46: / Line 39: @@
 ==Group Velocity vs. Phase Velocity==
-The book defines the group velocity as <math>v_g=\frac{d\omega}{dt}</math>, but what does that mean?  What is the group velocity?  What makes it different from the phase velocity?
+The book defines the group velocity as <math>v_g=\frac{d\omega}{dk}</math>, but what does that mean?  What is the group velocity?  What makes it different from the phase velocity?
 The real part of the wavefunction of a wave packet looks like a sinusoidal function bound within an envelope.  The wavefunction can move faster or slower than the envelope.  The speed of the envelope is the group velocity, and the speed of the waves inside the envelope is the phase velocity.

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