Rippletank simulations: DoubleSlit Interference
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Illustration of doubleslit interference
Conditions and pertinent physics
 Point Sources A pair of point sources are in phase and
each radiate outgoing circular waves. The pointsources are
positioned at (1,0) and (+1,0) in the coordinate system shown.
 Superposition The two separate outgoing circular wave patterns
overlap in space and therefore interfere.
 Interference Due to destructive interference,
nodes are
created. Similarly, constructive interference gives rise to
antinodes.
Any point on an antinode is nearer to one source than the other by
exactly m wavelengths where m is an integer.
This makes the two waves add in phase (and therefore tend
to reinforce each other).
Any point on a node is nearer to one source than the other by
exactly (m + 1/2) wavelengths where m is
an integer.
This makes the two waves add 180° out of phase (and
therefore tend to cancel).
3D view of the above.
Questions:
In the animation above:

Far from the sources, the nodes and antinodes are
lines which appear to diverge from the origin at specific
angles (meaure angle relative to the original ``forward'' direction
which in this case is y dir). Identify all of the nodes and
antinodes
in the above simulation. Label them appropriately (e.g., m = 0,
m =+1,
etc.)
 Determine the wavelength l and the value
of d (separation between the pointsources) for the above
simulation through a careful examination of the figure. (Assume
the axes are calibrated in meters.)
 Based on the wavelength and d values, compute the
angles for all antinodes shown in the figure. Repeat for all
nodes. Compare your results to the actual geometry of the figure.
© 2000 R. J. Hauenstein. All rights reserved.
(Courseware for PHYS 2414, Fall semester, 2000, Oklahoma
State University.)
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