|The phase of the wave is moving from bottom right to
while the wave group is traveling from top right to bottom left.
Brunt-Väisälä frequency: 3.9 sec.
Oscillation period: 5.5 sec.
f=135mm, F4.5, 1/15 seconds, ASA400, 2mm slit used.
5mm slit used.
Speeded up 10 times.