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

Disk (mathematics)

In geometry, a disk (also spelled disc) is the region in a plane bounded by a circle. A disk is said to be closed or open according to whether it contains the circle that constitutes its boundary.

Formulas

In Cartesian coordinates, the open disk of center and radius R is given by the formula

while the closed disk of the same center and radius is given by

The area of a closed or open disk of radius R is πR² (see area of a disk).

Properties

The disk has circular symmetry.

The open disk and the closed disk are not topologically equivalent (that is, they are not homeomorphic), as they have different topological properties from each other. For instance, every closed disk is compact whereas every open disk is not compact. However from the viewpoint of algebraic topology they share many properties: both of them are contractible and so are homotopy equivalent to a single point. This implies that their fundamental groups are trivial, and all homology groups are trivial except the 0th one, which is isomorphic to Z. The Euler characteristic of a point (and therefore also that of a closed or open disk) is 1.

Disc (telefilm)

Disc is a Bangladeshi science fiction television film directed by Farhad Ahmed and produced by Rejaul Haque and Sabbir Chowdhury under the banner of Eagle Entertainment and Boomerang. The telefilm stars Ziaul Faroque Apurbo and Zakia Bari Momo is lead role while Sanj John was featured as the main antagonist. The television film was aired on NTV during Eid Ul Adha, 25 September 2015.

Cast

Plot

The intro starts with narrator explaining how extraterrestrial life from other planets are watching over the earth. The telefilm stars with a man reporting a missing car to the police station, explaining how his car suddenly disappeared. It later turns out Faheem (Apurbo), the main protagonist of the story took the car. Apurbo is a mysterious character who have an obsession with extraterrestrial life. As he drives through the city with the stolen car, he gets stopped by the Police, while Police inquires him about the car, he hallucinates their mind and leaves.