Airy beam

An Airy beam is a non-diffracting waveform which gives the appearance of curving as it travels.

Physical description

A cross section of an ideal Airy beam would reveal an area of principal intensity, with a series of adjacent, less luminous areas trailing off to infinity. In reality, the beam is truncated so as to have a finite composition.

As the beam propagates, it does not diffract, i.e., does not spread out. The Airy beam also has the characteristic of freely accelerating. As it propagates, it bends so as to form a parabolic arc.

History

The term "Airy beam" derives from the Airy integral, developed in the 1830s by Sir George Biddell Airy to explain optical caustics such as those appearing in a rainbow.

The Airy waveform was first theorized in 1979 by M. V. Berry and Nándor L. Balázs. They demonstrated a nonspreading Airy wave packet solution to the Schrödinger equation.

In 2007 researchers from the University of Central Florida were able to create and observe an Airy beam for the first time in both one- and two-dimensional configurations. The members of the team were Georgios Siviloglou, John Broky, Aristide Dogariu, and Demetrios Christodoulides.

Airy

Airy may refer to:

Airy (Martian crater)

Airy is an impact crater on Mars, named in honor of the British Astronomer, Royal Sir George Biddell Airy (1801–1892). The crater is approximately 43 kilometres (27 mi) in diameter and is located at 0.1°E 5.1°S in the Meridiani Planum region. The much smaller crater Airy-0, which defines the location of Mars' prime meridian, lies within it.

References

Airy (lunar crater)

Airy is a lunar impact crater located in the southern highlands. It is named in honour of British astronomer George Biddell Airy. It forms the southern-most member of a chain of craters consisting of Vogel, Argelander, and Airy. A little further to the south lies Donati. Airy has a worn, and somewhat polygonal rim that it broken at the northern and southern ends. It has an irregular floor and a central peak.

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Airy.

References

Beam

Beam may refer to:

BEAM

Beam (music)

In musical notation, a beam is a horizontal or diagonal line used to connect multiple consecutive notes (and occasionally rests) in order to indicate rhythmic grouping. Only eighth notes (quavers) or shorter can be beamed. The number of beams is equal to the number of flags that would be present on an un-beamed note.

Grouping

The span of beams indicates the rhythmic grouping, usually determined by the time signature. Therefore, beams do not usually cross bar lines, or major sub-divisions of bars. If notes extend across these divisions, this is indicated with a tie.

In modern practice beams may span across rests in order to make rhythmic groups clearer.

In vocal music, beams were traditionally used only to connect notes sung to the same syllable. In modern practice it is more common to use standard beaming rules, while indicating multi-note syllables with slurs.

Positioning

Notes joined by a beam usually have all the stems pointing in the same direction (up or down). The average pitch of the notes is used to determine the direction – if the average pitch is below the middle staff-line, the stems and beams usually go above the note head, otherwise they go below.

Beam (nautical)

The beam of a ship is its width at the widest point as measured at the ship's nominal waterline. The beam is a bearing projected at right-angles from the fore and aft line, outwards from the widest part of ship. Beam may also be used to define the maximum width of a ship's hull, or maximum width plus superstructure overhangs.

Generally speaking, the wider the beam of a ship (or boat), the more initial stability it has, at expense of reserve stability in the event of a capsize, where more energy is required to right the vessel from its inverted position.

Typical values

Typical length-to-beam ratios for small sailboats are from 2:1 (dinghies to trailerable sailboats around 20 ft or 6 m) to 5:1 (racing sailboats over 30 ft or 10 m).

Large ships have widely varying beam ratios, some as large as 20:1.

Rowing shells designed for flatwater racing may have length to beam ratios as high as 30:1, while a coracle has a ratio of almost 1:1 – it is nearly circular.

Formula

The beam of many monohull vessels can be calculated using the following formula: