Interference:

Assume that you are a surfer. You spend the winter on the north shore of Oahu. In maritime sub-Arctic, storms show off across the Pacific, spinning off from a parent vortex close to the Kamchatka peninsula. You see the satellite images of these storms on the Internet. The Kamchatka low is steady and strong, breeding systems which swoop southeastward and vent their fury in the North America. Swells are pushed across the whole Pacific from these storms; there is nothing among the storm tracks and the shores of Hawaii. The swells appear at places such as Pipeline and break over coral and sand, attainment heights which frequently exceed 5 m (i.e., 16 ft). Trade winds blow from east to west, generating smaller swells across the big ones. The gusts of wind and local squalls add chop. On a fine day-the type you, as a surfer, live for-the storm swell is tough, and the wind is light. You can ride the big breakers without being bumped about by the small stuff. On a terrible day, waves pile onto waves in a random way. The main swell is as big and well defined as on a fine day, though the interference makes surfing very hard.

Whenever two major marine storms are divided by a great distance, each generating important swells, things get fascinating. These conditions are more likely to attract scientists than surfers. This type of circumstances can take place during the winter on the north shore of Oahu, though it is more frequently found in the tropics during the hurricane season. Tropical storms generate some of the biggest surf in the world. Whenever a hurricane prowls the sea, swells radiate in mounting circles from the storm's central vortex. When two storms of same size and intensity are divided by a vast distance, complicated swell patterns span millions of square kilometers. Among the storms, swells alternately cancel and reinforce each other, generating wild seas.

Interference patterns formed by multiple wave sources emerge at all scales, from swells at sea to sound waves in a concert hall, from radio broadcast towers to the holographic apparatus. The small change in the associative positions or wavelengths of two sources can make a profound difference in the manner the composite pattern emerges. Illustrations are shown in figures shown below.

Figure: A slight source displacement can change an interference pattern dramatically. Note that the difference among the pattern created by the intersecting lines in part a, as compared with the pattern in portion b.

Figure: Alike wavelength (a) versus a 10 % difference (b). Note that the difference in the interference pattern caused by the wavelength change.

Assume that the two tropical storms are sweeping about the Atlantic basin, steered by currents in the upper environment. The interference pattern generated by their swells grows from moment to moment. The multiple crests and troughs plot along a front hundreds of kilometers long: a rogue wave. These monster waves can capsize sea liners and freighters. Veteran sailors tell stories regarding walls of water which break in the open ocean, seeming to challenge the laws of hydrodynamics.

The wave interference on high oceans, whereas potentially frightening in its proportions, is not simple for scientists to examine. Patterns are at times seen from aircraft, and complicated radar can disclose subtleties of the surface, though seas do not lend themselves to controlled experiments. Nor you can go out in a boat and sail into storm-swell interference patterns and expect to return with significant data, though you may end up with stories to tell your grand children when you survive. Though, there are manners which even a child can conduct unforgettable experiments with wave interference and convergence.

The soap bubbles, with their rainbow-colored surfaces, are tailor made for this. The visible-light waves add and cancel across the visible spectrum, reflecting from the outer and inner surfaces of the soap film and teasing the eye with green, red, violet, and then red again.

The adults can play with wave interference, also. Any building with a large rotunda gives a perfect venue. According to legend, long ago in the halls of Congress, some elected officials were able to eavesdrop on certain assumedly private whisperings since the vast dome overhead reflected and focused the sound waves from one politician's mouth to another's ears.