Ripple tank demos for radio astronomy and interferometry

ripple_tank_demos.txt

# Ripple Tank Demos
Website available at: http://www.falstad.com/ripple/ . Copy and paste the following entries
by going under "File -> Import From Text...", beginning from the "$" until the blank line.
One can use the two check-boxes on the right to stop the simulation and visualize the
amplitdues in 3D. The sliders on the right can be used to adjust the rate/speed of the
simulation and wavelength/frequency of the wave (under "Source Frequency").

Single point source. Point source limits to plane wave.
$ 1 512 64 10 0 668 0.048828125
s 2 257 45 0 0.466666 0 10 100 1 0

Two point sources. Double slit analog and constructive/destructive interference.
$ 1 512 64 10 0 689 0.048828125
s 2 219 51 0 0.466666 0 10 100 1 0
s 2 290 51 0 0.466666 0 10 100 1 0

Focused wavepacket. A wavepacket is focused by a parabolic reflector, see in 3D to see increase in intensity.
$ 1 640 80 10 0 466 0.048828125
p 0 54 479 568 597 0
S 2 21 70 621 70 2 0.4999466723549488 0 2.944190050882948 883.2570152648844 1 0
P 1 312 456
P 1 164 252

Primary beam. A parabolic reflect acting as a transmitter. Vary the frequency to change the width of the main lobe.
$ 1 512 64 10 1 738 1.5625e-8
p 0 173 459 340 499 0
s 2 256 455 0 1.166665 0 10 100 1 0

Two element interferometer. Offset plane wave arriving at two parabolic reflectors. Traces show phase offset between antennas. The measured phase difference can be used to determine the angle.
$ 1 512 64 10 0 411 0.048828125
p 0 86 435 215 460 0
p 0 288 435 415 460 0
S 2 2 61 509 5 0 0.5 0 10 100 1 0
P 1 150 424
P 1 352 424

Slab in the sky. A line-source produces a bessel function in the far-field (equivalent to single slit).
$ 1 1007 125 10 0 654 0.039721946375372394
S 2 450 48 559 48 0 1.166665 0 10 100 1 0
P 1 499 994
P 1 384 994

Resolving two sources. Two point sources are in the sky. For two antennas close together, it appears as a plane wave, but the intensities will roll off and eventually reach the first null.
$ 1 1007 125 10 0 654 0.039721946375372394
P 1 499 994
P 1 384 994
s 2 503 54 0 0.5 0 10 100 1 0
s 2 545 54 0 0.5 0 10 100 1 0