Group Velocity / Phase Velocity Animation - Case 3: Negative Group Velocity | Part 3

[@imadiixq.8060]

this is a wave packet , combination of three waves ??

[@meyavuz]

+ImaDiiX Q. yes

[@bakuazerbaycan3340]

its very interesting. in which software you do it? I want to repeat.

[@meyavuz]

It is done by Matlab.

[@willeett]

Can we have the code?

[@5emeLaHulpe]

Case 4 : Positive group and negative phase velocities ?

[@meyavuz]

:) Sure, why not? I will try that. Thanks

[@Souravkumar-iw7gy]

can u please explain how to get the simulation on my own

[@meyavuz]

Add multiple sinusoids with different frequencies (sin(2*pi*f*t) where f is the frequency) and plot them at different time instants.

[@ericcortial4590]

can you explain this phenomenon ? I don't really understand...

[@meyavuz]

Basically three different waves are summed up which provides a final wave packet which has a certain group and phase velocity. You can check the other ones in the session to see how different waves can interact to create different group and phase velocity combinations. Let me know what exactly you want explanation for so that I can help further. Thanks

[@monakamel97]

@@meyavuz what does it mean for a wave to have negative or zero group velocity ?

[@meyavuz]

@@monakamel97 If we were to assume these are sea waves, in the zero group velocity which is the velocity of the whole packet (combination of all underlying waves) would be zero, i.e. an object on the sea surface would not move laterally but just go up and down vertically. In the negative group velocity, the object on the sea surface would move in the opposite direction to each underlying wave.

[@meyavuz]

@@monakamel97 For the negative group velocity check this MIT video for 10 seconds or so. He explains it using Michael Jackson's moonwalk.

[@fehmi35]

@@meyavuz hello. If It is em wave and the group velocity is negative like in the video, will the electron in the +x direction move in -x direction ?