Airy disk

In optics, the Airy disk (or Airy disc) and Airy pattern are descriptions of the best focused spot of light that a perfect lens with a circular aperture can make, limited by the diffraction of light. The Airy disk is of importance in physics, optics, and astronomy.

The diffraction pattern resulting from a uniformly-illuminated circular aperture has a bright region in the center, known as the Airy disk which together with the series of concentric bright rings around is called the Airy pattern. Both are named after George Biddell Airy. The disk and rings phenomenon had been known prior to Airy; John Herschel described the appearance of a bright star seen through a telescope under high magnification for an 1828 article on light for the Encyclopedia Metropolitana:

...the star is then seen (in favourable circumstances of tranquil atmosphere, uniform temperature, &c.) as a perfectly round, well-defined planetary disc, surrounded by two, three, or more alternately dark and bright rings, which, if examined attentively, are seen to be slightly coloured at their borders. They succeed each other nearly at equal intervals round the central disc....

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

Disc

Disc or disk (computing and American English) may refer to:

Data storage

Everytime You Touch Me

"Everytime You Touch Me" is a song by American electronica musician Moby, released as the third single from his album Everything Is Wrong. The vocals of "Everytime You Touch Me" are performed by Rozz Morehead and Kochie Banton, both of whom appear on Moby's previous single, "Feeling So Real". Before the release of the "Everytime You Touch Me" single, a remix competition was held. The winning remix, made by Jude Sebastian, is featured as track three on the single.

Track listing

Disk storage

Disk storage is a general category of storage mechanisms where data are recorded by various electronic, magnetic, optical, or mechanical changes to a surface layer of one or more rotating disks. A disk drive is a device implementing such a storage mechanism. Notable types are the hard disk drive (HDD) containing a non-removable disk, the floppy disk drive (FDD) and its removable floppy disk, and various optical disc drives and associated optical disc media.

(The spelling disk and disc are used interchangeably except where trademarks preclude one usage, e.g. the Compact Disc logo. The choice of a particular form is frequently historical, as in IBM's usage of the disk form beginning in 1956 with the "IBM 350 disk storage unit").

Background

Audio information was originally recorded by analog methods (see Sound recording and reproduction). Similarly the first video disc used an analog recording method. In the music industry, analog recording has been mostly replaced by digital optical technology where the data are recorded in a digital format with optical information.