Ripple-tank simulations: Double-Slit Interference
Illustration of double-slit interference
Conditions and pertinent physics
3-D view of the above.
- Point Sources A pair of point sources are in phase and
each radiate outgoing circular waves. The point-sources 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,
created. Similarly, constructive interference gives rise to
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
This makes the two waves add 180° out of phase (and
therefore tend to cancel).
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
in the above simulation. Label them appropriately (e.g., m = 0,
- Determine the wavelength l and the value
of d (separation between the point-sources) 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
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