Internal Gravity Wave

Observing the relationship between
group velocity and phase velocity

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14 sec. after start


40 sec. after start


66 sec. after start

The phase of the wave is moving from bottom right to top left,
while the wave group is traveling from top right to bottom left.

Experimental conditions

Brunt-Väisälä frequency: 3.9 sec.
Oscillation period: 5.5 sec.
Amplitude: 0.6cm

Photographic conditions

f=135mm, F4.5, 1/15 seconds, ASA400, 2mm slit used.

Filming conditions

5mm slit used.
Speeded up 10 times.
240x180:15fps, 320x240:30fps