Dispersion Flashcards
1
Q
The group velocity is
A
the velocity with which the maximum amplitude of the group propagates. It is the velocity of energy transmission by the group.
2
Q
if vg = c
A
then there is no dispersion
3
Q
if vg < c
A
we get normal dispersion
4
Q
if vg > c
A
we get anomalous dispersion
5
Q
Why does dispersion matter
A
If the frequency components of our signal do not all propagate at the same speed then the pulse will get smeared out making detection impossible.
6
Q
Neighbouring spring extensions
A
K(exp[-ik aₙ₊₁]-2exp[-ikaₙ]+exp[-ikaₙ₋₁] = m(iω)^2 exp[-ikaₙ]
7
Q
the dispersion relation
A
ω ~ k [ a √ K/m ]
