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F

Definition: F

F

1. F is the sixth letter of the English alphabet, and a nonvocal consonant. Its form and sound are from the Latin. The Latin borrowed the form from the Greek digamma /, which probably had the value of English w consonant. The form and value of Greek letter came from the Phoenician, the ultimate source being probably Egyptian. Etymologically f is most closely related to p, k, v, and b; as in E. five, Gr. pe`nte; E. wolf, L. lupus, Gr. ly`kos; E. fox, vixen ; fragile, break; fruit, brook, v. t.; E. bear, L. ferre. See Guide to Pronunciation, // 178, 179, 188, 198, 230.

Transitive verb

1. The name of the fourth tone of the model scale, or scale of C. F sharp (F /) is a tone intermediate between F and G.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Date "F" was first used in popular English literature: sometime before 1350. (references)

 

Specialty Definition: F

DomainDefinition

Literature

F F is written on his face. "Rogue" is written on his face. The letter F used to be branded near the nose, on the left cheek of felons, on their being admitted to "benefit of clergy." The same was used for brawling in church. The custom was not abolished by law till 1822. Source: Brewer's Dictionary.

Space

Force. (references)

Source: compiled by the editor from various references; see credits.

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Specialty Definition: ATP synthase

(From Wikipedia, the free Encyclopedia)

An ATP synthase is a general term for an enzyme that can synthesize adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and inorganic phosphate by utilizing some form of energy. The overall reaction sequence is:

ADP + Pi → ATP

These enzymes are of crucial importance in almost all organisms, because ATP is the common "energy currency" of cells.

In mitochondria, the F0F1 ATP synthase has a long history of scientific study. The F1 portion of the ATP synthase is above the membrane, the F0 portion is within the membrane. It's easy to visualize the F0F1 particle as resembling the fruiting body of a common mushroom, with the head being the F1 particle, the stalk being the gamma subunit of F1, and the base and "roots" being the F0 particle embedded in the membrane. The F1 particle was first isolated by Ephraim Racker in 1961.

The F1 particle is large and can be seen in the transmission electron microscope by negative staining (1962, Fernandez-Moran et al., Journal of Molecular Biology, Vol 22, p 63). These are particles of 90 Å diameter that pepper the inner mitochondrial membrane. They were originally called elementary particles and were thought to contain the entire respiratory apparatus of the mitochondrion, but through a long series of experiments, Ephraim Racker and his colleagues were able to show that this particle is correlated with ATPase activity in uncoupled mitochondria and with the ATPase activity in submitochondrial particles created by exposing mitochondria to ultrasound. This ATPase activity was further associated with the creation of ATP by yet another long series of experiments in many laboratories.

In the 1960s through the 1970s, Paul Boyer developed his binding change, or flip-flop, mechanism, which postulated that ATP synthesis is coupled with a conformational change in the ATP synthase generated by rotation of the gamma subunit. John E. Walker crystallized the ATP synthase and was able to determine that Boyer's conformational model was essentially correct. In the crystal structure, the F1 particle can be seen to be composed of a cylinder of 6 subunits, alternating alpha and beta subunits, that form a ring around an asymmetrical gamma subunit. Facilitated diffusion of protons causes the F0 particle to rotate, rotating the gamma subunit of F1, while the major F1 subunits are fixed in place. This rotation forces a conformational change in the F1 particle, eventually leading to the synthesis of ATP. For elucidating this Boyer and Walker shared in the 1997 Nobel Prize in Chemistry.

The F1 particle is a reversible ATP synthase. Large enough quantities of ATP cause this particle to create a proton gradient. Under physiological conditions, this particle generally runs in the opposite direction, creating ATP while using the protonmotive force created by the electron transport chain as a source of energy. The overall process of creating energy in this fashion is termed oxidative phosphorylation.

A similar particle is found in chloroplasts, the CF1 particle, also a reversible ATP synthase. However, the chloroplast thylakoid membranes are inverted in "F1 topology" relative to mitochondria (the CF1 particles are on the outside) and in this sense chloroplasts more resemble submitochondrial particles.

See also:

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Casualties of the September 11, 2001 Terrorist Attacks

(From Wikipedia, the free Encyclopedia)

Any tributes to the individuals lost in this tragedy are welcome and encouraged at our memorial site. Some articles originally posted to wikipedia have been moved there - if you are looking for such an article, please check there.

See also Missing Persons, Foreign casualties, and Survivors.

Casualties

Planes - World Trade Center - Pentagon
A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

As of October 29, 2003, 2,995 people were presumed dead as a result of all four September 11 attacks. This includes the casualties at the World Trade Center, the Pentagon, on the airplanes and the hijackers.

Planes

265 people killed on four planes; 232 passengers, 25 flight attendants, 8 pilots. (Note that this total includes the 19 hijackers, who reportedly boarded the planes as passengers.)

See also: Memorial wiki tributes to the occupants of each plane

World Trade Center

By October 29, 2003, 2605 people were listed as confirmed dead and 1058 bodies had been identified. (Note: this total does not include the 127 passengers and 20 crew on the two aircraft or the 10 hijackers).

The listing and memorial.

See also:

Missing Persons

The number of missing people grew to estimates as high as over 6000 in the months following the attack, but steadily declined as stories were checked and duplicate entries removed. (See Timeline of WTC missing).

As of August 2002, there were approximately 90 people who were officially missing; that is, their remains had not been identified and no family members had requested a death certificate.

Detailed listing.

Survivors

The great majority of the over 40,000 people working at the World Trade Center at the time of the attack evacuated safely, including 18 who escaped from above the impact zone in the second tower hit. By 9/20/2001 6291 people, including rescue and recovery workers, had been treated for injuries.

Detailed listing.

Pentagon

The Pentagon reports 125 staffers killed or missing, with 121 remains recovered and identified, as of Sept. 11, 2002. At least one person died later as a result of wounds incurred.

The listing and memorial.

Missing Persons

The Pentagon reports 4 staffers missing. One passenger on the airliner which hit the Pentagon was also never identified.

Detailed listing.

Survivors

88 treated at hospital.

Detailed entry.

Victim legends

Due to the very large number of World Trade Center casualties and missing persons, victim legends were a common form of September 11, Terrorist Attack urban legends. These were tales of victims who did not exist, spread by word-of-mouth and the Internet. Official sites, such as http://www.september11victims.com, contain accurate entries and are trusted content. Because Wikipedia, and many other websites allowed freely adding victims, there were no doubt many obvious fake entries. Fake victims added to these lists were often simply missing at the time of the attacks, or actually survivors of the attacks.

See also

September 11, 2001 Terrorist Attack - Donations - Assistance - Memorials and Services

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Casualties of the September 11, 2001 Terrorist Attacks."

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F

(From Wikipedia, the free Encyclopedia)

The sixth letter of the Latin alphabet, F developed from the digraph FH that stood for /f/.

A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z

The Etruscans were the inventors of this digraph; F on its own stood for /w/ in Etruscan as in Greek (where the letter F ? called Digamma in Greek ? has disappeared due to the fact that the /w/ phoneme itself disappeared.) The origin of F is the Semitic letter wâw that also represented /w/ and originally probably represented a hook or a club.

Foxtrot represents the letter F in the NATO phonetic alphabet.

F is also:

Two-letter combinations starting with F:

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F4 (mathematics)

(From Wikipedia, the free Encyclopedia)

F4 is the name of a Lie group (and also its Lie algebra). It is one of the exceptional simple Lie groups.

Roots of F4

Simple roots

Weyl/Coxeter group

Its Weyl/Coxeter group is the symmetry group of the 24-cell.

Cartan matrix

See also Simple Lie group, Lie group, Weyl group, Dynkin diagram.

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "F4 (mathematics)."

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Fahrenheit

(From Wikipedia, the free Encyclopedia)

Alternate meaning: Fahrenheit graphics API

The degree Fahrenheit is a unit of temperature named for the German physicist Daniel Gabriel Fahrenheit, who proposed it in 1724. In the Fahrenheit scale of temperature, the freezing point of water is 32 degrees, and the boiling point is 212 degrees. Hence a degree Fahrenheit is 5/9ths of a kelvin or degree Celsius, and -40 degrees Fahrenheit is equal to -40 degrees Celsius.

Fahrenheit established zero degrees as the temperature at which an equal mixture of ice and salt melts (some say he took that fixed mixture of ice and salt that produced the lowest temperature); and ninety-six degrees as the temperature of a healthy human body. Initially, his scale had only contained 12 equal subdivisions, but then later he divided each division into 8 equal degrees ending up with 96. He then observed that plain water would freeze at 32 degrees and boil at 212 degrees.

His measurements were not entirely accurate, though; by his original scale, the actual freezing and boiling points would have been slightly different than 32 and 212. Some time after his death, the error was discovered, and it was decided to recalibrate the scale with 32 and 212 being the actual freezing and boiling points of plain water. This resulted in the healthy human body temperature being 98.6 degrees rather than 96.

The Fahrenheit scale was widely used in Europe until a switch to the Celsius (formerly centigrade) scale (for the conversion formulas, see that article). It is still used by the general population for everyday temperature measurement in the United States and a declining number of other English-speaking countries.

Other temperature scales include the Réaumur (1730), Rømer (1730+), kelvin (1862), and Rankine (ca. 1860). (Note that "kelvin" is lower-cased because it is an SI unit, even though it is named after a person).

External link

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Fahrenheit."

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Farad

(From Wikipedia, the free Encyclopedia)

The farad is the SI unit of capacitance (named after Michael Faraday). A capacitor has a value of one farad when one coulomb of charge causes a potential difference of one volt across it. Its dimensions in SI units are:

Since the farad is a very large unit, values of capacitors are usually expressed in microfarads (μF), nanofarads (nF), or picofarads (pF). The farad should not be confused with the faraday, an older unit of charge nowadays deprecated in favour of the coulomb.

See also

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F-block

(From Wikipedia, the free Encyclopedia)

F-block (for fundamental) elements consist of the lanthanide and actinide series. They have two s-electrons in their outer (n) electron shell and f-electrons in their inner (n-2) shell. Some also have d-electrons in their semi-inner (n-1) shell.

Other blocks:

See also: Electron configuration

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "F-block."

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Fibonacci number

(From Wikipedia, the free Encyclopedia)

In mathematics, the Fibonacci numbers form a sequence defined recursively by the following equations:

F(0) = 0
F(1) = 1
F(n + 2) = F(n) + F(n + 1) for all n ≥ 0.

Alternatively the recurrence can be given by
F(0) = 1
F(1) = 1
F(n) = F(n-1) + F(n-2)
This definition may be more common, but it is equivalent to the one above up to a shift of indices.

In words: you start with two ones, and then produce the next Fibonacci number by adding the two previous Fibonacci numbers. The first Fibonacci numbers are

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657...
This sequence was first described by Leonardo of Pisa, who was known as Fibonacci (ca. 1200), to describe the growth of a rabbit population. The numbers describe the number of pairs in a (somewhat idealized) rabbit population after n months if it is assumed that The formula above applies to the rabbit problem because if in month n we have "a" rabbits and in month n+1 we have "b" rabbits then in month n+2 we'll necessarily have a+b rabbits. That's because we know each rabbit basically gives birth to another each month (actually each pair gives birth to another pair, but it's the same thing) and that means that all "a" rabbits give birth to another number of "a" rabbits which will become fertile after two months, which is exactly at month n+2. That's why we have the population at moment n+1 (which is "b") plus exactly the population at moment n (which is "a").

Explicit formula

The term Fibonacci sequence is also applied more generally to any function g where g(n + 2) = g(n) + g(n + 1). These functions are precisely those of the form g(n) = aF(n) + bF(n + 1) for some numbers a and b, so the Fibonacci sequences form a vector space with the functions F(n) and F(n + 1) as a basis.

As was pointed out by Johannes Kepler, the growth rate of the Fibonacci numbers, that is, F(n + 1) / F(n), converges to the golden mean, denoted φ. This is the positive root of the quadratic equation x2 - x - 1 = 0, so φ2 = φ + 1. If we multiply both sides by φn, we get φn+2 = φn+1 + φn, so the function φn is a Fibonacci sequence. The negative root of the quadratic, 1 - φ, can be shown to have the same properties, so the two functions φn and (1-φ)n form another basis for the space.

By adjusting the coefficients to get the proper initial values F(0) = 0 and F(1) = 1, we obtain

This result can also be derived using the technique of generating functions, or the technique of solving linear recurrence relations.

As n goes to infinity, the second term converges to zero, so the Fibonacci numbers approach the exponential φn / √5, hence their convergent ratios. In fact the second term starts out small enough that the Fibonacci numbers can be obtained from the first term alone, by rounding to the nearest integer.

Computing Fibonacci numbers

Computing Fibonacci numbers by computing powers of the golden mean is not very practical except for small values of n, since rounding errors will accrue and floating point numbers usually don't have enough precision.

The straightforward recursive implementation of the Fibonacci sequence definition is also not advisable, since it would compute many values repeatedly (unless the programming language has a feature which allows the storing of previously computed function values). Therefore, one usually computes the Fibonacci numbers "from the bottom up", starting with the two values 0 and 1, and then repeatedly replacing the first number by the second, and the second number by the sum of the two.

For huge arguments and if a bignum system is being used, a faster way to calculate Fibonacci numbers uses the following matrix equation:

and employs exponentiating by squaring.

Applications

The Fibonacci numbers are important in the run-time analysis of Euclid's algorithm to determine the greatest common divisor of two integers.

Matiyasevich was able to show that the Fibonacci numbers can be defined by a Diophantine equation, which led to his original solution of Hilbert's tenth problem.

The Fibonacci numbers occur in a formula about the diagonals of Pascal's triangle (see binomial coefficient).

An interesting use of the Fibonacci sequence is for converting miles to kilometers. For instance, if you want to know about how many kilometers 5 miles is, take the Fibonacci number (5) and look at the next one (8). 5 miles is about 8 kilometers. This works because it so happens that the conversion factor between miles and kilometers is roughly equal to φ.

A logarithmic spiral can be approximated as follows: start at the origin of the cartesian coordinate system, move F(1) units to the right, move F(2) units up, move F(3) units to the left, move F(4) units down, move F(5) units to the right etc. This is similar to the construction mentioned in the golden mean article. Fibonacci number s often occur in nature when logarithmic spirals are built from discrete units, such as in sunflowers or in pine cones.

Generalizations

A generalization of the Fibonacci sequence are the Lucas sequences. One kind can be defined thus:

L(0) = 0
L(1) = 1
L(n+2) = PL(n+1) + QL(n)

where the normal Fibonacci sequence is the special case of P = Q = 1. Another kind of Lucas Sequence begins with L(0) = 2, L(1) = P. Such sequences have applications in number theory and primality proving.

Algorithm

Fibonacci numbers can be calculated by following Scheme code: 
(define fab

 (lambda (x)
   (if (< x 2)
     x
     (+ (fab (- x 1)) (fab (- x 2))))))

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Fibonacci number."

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Film

(From Wikipedia, the free Encyclopedia)

Initially, moving pictures meant only the movement that is perceived when a string of celluloid-recorded images are projected at a rate of about 16 or more frames per second (see persistence of vision). Today, motion pictures (or "movies") are an art form, as well as one of the most popular forms of entertainment.

A feature film is usually defined as being more than 60 minutes in length.

Opportunities to see a feature film include:

History of cinema

Originally moving picture film was shot at various speeds using hand-cranked cameras; then the speed for mechanized cameras and projectors was standardized at 16 frames per second, which was faster than much existing hand-cranked footage. A new standard speed, 24 frames per second, came with the introduction of sound. Improvements since the late 1800s include the mechanization of cameras, allowing them to record at a consistent speed, the invention of more sophisticated filmstocks and lenses, allowing directors to film in increasingly dim conditions, and the development of synch sound, allowing sound to be recorded at exactly the same speed as its corresponding video. Since the advent of many other media technologies, film may include a broad range of media — both linear and non-linear, dramatic and informational, motion and still (though progressive).

List of movie-related topics

Film people

Actors
Film crew
film criticism
Film directors
Screenwriter
Movie studio
Experimental filmmaker
Louis Aimé Augustin Le Prince
Etienne-Jules Marey

Classification by chronology

List of 'years in film'
1960s movies
1970s movies
1980s movies
1990s movies
2000s movies

Classification by geographical location of production

External links, references, and resources

 simple:Cinema

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Film."

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Fluorine

(From Wikipedia, the free Encyclopedia)

Oxygen - Fluorine - Neon
 
F
Cl  
 
 

Full table
General
Name, Symbol, NumberFluorine, F, 9
Series Halogens
Group, Period, Block17 (VIIA), 2 , p
Density, Hardness 1.696 kg/m3 (273 K), NA
Appearance pale greenish-yellow gas
Atomic Properties
Atomic weight 18.9984 amu
Atomic radius (calc.) 50 (42) pm
Covalent radius 71 pm
van der Waals radius 147 pm
Electron configuration [He]2s2s2 2p5
e- 's per energy level2, 7
Oxidation states (Oxide) -1 (strong acid)
Crystal structure cubic
Physical Properties
State of matter Gas (nonmagnetic)
Melting point 53.53 K (-363.32 °F)
Boiling point 85.03 K (-306.62 °F)
Molar volume 11.20 ×1010-3 m3/mol
Heat of vaporization 3.2698 kJ/mol
Heat of fusion 0.2552 kJ/mol
Vapor pressure no data
Speed of sound no data
Miscellaneous
Electronegativity 3.98 (Pauling scale)
Specific heat capacity 824 J/(kg*K)
Electrical conductivity no data
Thermal conductivity 0.0279 W/(m*K)
1st ionization potential 1681.0 kJ/mol
2nd ionization potential 3374.2 kJ/mol
3rd ionization potential 6050.4 kJ/mol
4th ionization potential 8407.7 kJ/mol
5th ionization potential 11022.7 kJ/mol
6th ionization potential 15164.1 kJ/mol
7th ionization potential 17868 kJ/mol
8th ionization potential 92038.1 kJ/mol
9th ionization potential 106434.3 kJ/mol
Most Stable Isotopes
isoNAhalf-life DMDE MeVDP
19F100%F is stable with 10 neutrons
SI units & STP are used except where noted.
Fluorine is a chemical element in the periodic table that has the symbol F and atomic number 9. It is a poisonous pale yellow, univalent gaseous halogen that is the most chemically reactive and electronegative of all the elements. In its pure form, it is highly dangerous, causing severe chemical burns on contact with skin.

Notable Characteristics

Pure fluorine is a corrosive pale yellow gas that is a powerful oxidizing agent. It is the most reactive and electronegative of all the elements, and forms compounds with most other elements, including the noble gases xenon and radon. Even in dark, cool conditions, fluorine reacts explosively with hydrogen. In a jet of fluorine gas, glass, metals, water and other substances burn with a bright flame. It always occurs combined and has such an affinity for most elements, especially silicon, that it can neither be prepared nor kept in glass vessels.

In solution, fluorine commonly occurs as the fluoride ion F-. Fluorides are compounds that combine this fluoride ion with some positively charged radical.

Applications

Fluorine is used in the production of low friction plastics such as Teflon, and in halons such as Freon. Other uses:

Hydrofluoric acid (chemical formula HFF) is used to etch glass in light bulbs and other products.
  • Monoatomic fluorine is used for plasma ashing in semiconductor manufacturing.
  • Along with its compounds, fluorine is used in the production of uranium (from the hexafluoride) and in more than 100 different commercial fluorochemicals, including many high-temperature plastics.
  • Fluorochlorohydrocarbonss are used extensively in air conditioning and in refrigeration. Chlorofluorocarbons have been banned for these applications because they are suspected to contribute to the ozone hole. Both of these classes of compounds are potent greenhouse gases.
  • Sodium fluoride has been used as an insecticide, especially against cockroaches.
  • Some other fluorides are often added to toothpaste and (somewhat controversially) to municipal water supplies to prevent dental cavities.

    • Some researchers have studied elemental fluorine gas a possible rocket propellant due to its exceptionally high specific impulse.

    History

    Fluorine (L fluere meaning flow or flux) in the form of fluorspar was described in 1529 by Georigius Agricola for its use as a flux, which is a substance that is used to promote the fusion of metals or minerals. In 1670 Schwandhard found that glass was etched when it was exposed to fluorspar that was treated with acid. Karl Scheele and many later researchers, including Humphry Davy, Gay-Lussac, Antoine Lavoisier, and Louis Thenard all would experiment with hydrofluoric acid (some experiments would end in tragedy).

    This element was not isolated for many years after this due to the fact that when it is separated from one of its compounds it immediately attacks the remaining materials of the compound. Finally in 1886 fluorine was isolated by Henri Moissan after almost 74 years of continuous effort.

    The first commercial production of fluorine was for the atomic bomb Manhattan project in World War II where the compound uranium hexafluoride (UF6) was used to separate isotopes of uranium. This process is still is use today in nuclear power applications.

    Compounds

    Fluorine can often be substituted for hydrogen when it occurs in organic compounds. Through this mechanism, fluorine can have a very large number of compoundss. Fluorine compounds involving rare gases have been confirmed with fluorides of krypton, radon, and xenon. This element is recovered from fluorite, cryolite, and fluorapatite.

    See also: Fluorocarbon

    Precautions

    Fluorine and HF must be handled with great care and any contact with skin and eyes should be strictly avoided.

    Both elemental fluorine and fluoride ions are highly toxic. When it is a free element, fluorine has a characteristic pungent odor that is detectable in concentrations as low as 20 ppb. It is recommended that the maximum allowable concentration for a daily 8-hour time-weighted exposure is 1 ppm.

    However, safe handling procedures enable the transport of liquid fluorine by the ton.

    External Links

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    F-number

    (From Wikipedia, the free Encyclopedia)


    Detail of a camera showing f stop scale.

    In photography the f-number expresses the diameter of the diaphragm aperture in terms of the effective focal length of the lens. For example, f/16 represents a diaphragm aperture diameter that is one-sixteenth of the focal length.

    The higher the f-number, the less light is admitted through the lens.

    f stops are a way of representing a convenient sequence of f-numbers in a geometric progression. Each 'stop' is marked with its corresponding f-number, and represents a halving of the light intensity from the one before, corresponding to a decrease of the diaphragm aperture diameter by a factor of √2, and hence an halving of the area of the aperture.

    Modern lenses use a standard f stops scale that corresponds to the sequence of the powers of √2 : f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45 and f/64. (Note that the values of the ratios are rounded off, to make them easy to write down).

    Shutter speeds are arranged in a similar scale, so that one step in the shutter speed scale corresponds to one step in the f stop scale.

    Photographers sometimes express exposure ratios in terms of 'stops'. If we ignore the f-number markings, the f-stops make a logarithmic scale of exposure intensity. Given this interpretation, you can then think of taking a half-step along this scale, to make an exposure difference of "half a stop".

    Since all lenses absorb some portion of the light passing through them (particularly zoom lenses containing many elements), for exposure purposes a T-stop is sometimes used instead of f-stop. The T-numbers are adjusted so that the amount of light transmitted through the lens at a given T-stop is equal to that going through an ideal non-absorbing lens set at that f-stop.

    In practice the maximal aperture of a lens often differs from a power of √2, and is not one of the standard f-stops. For example, the sequence of F-stops on the lens depicted in the picture above has f-numbers of f/3.5, f/5.6, f/8, f/11, f/16 and f/22.

    Depth of field increases with f-stop; for an example of this relationship, visit the depth of field article.

    Picture sharpness also varies with f-stop. The optimal f-stop vary with the lens characteristics. For example, on modern standard lenses having 6 or 7 elements the sharpest image is obtained around f/5.6-f/8, while for older standard lenses having only 4 elements (Tessar formula) stopping to f/11 will give the sharpest image. The reason the sharpness is best at medium f-numbers is that the sharpness at high f-number is constrained by diffraction, whereas at low f-numbers lens faults known as aberrationss will dominate.

    As an example of the use of f-numbers, an approximately correct exposure will be obtained on a sunny day using ISO 125 film, an aperture of f/16 and a shutter speed of 1/125th of a second. This is called the "sunny f/16 rule".

    See also:

    External links

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    French language

    (From Wikipedia, the free Encyclopedia)

    French (la langue française) is one of the most important Romance languages, outnumbered only by Spanish and Portuguese. French is the 11th most spoken language in the world, spoken by about 77 million people as a mother tongue, and 128 million including second language speakers, in 1999. It is an official or administrative language in various communities and organizations (such as the European Union, IOC, United Nations and Universal Postal Union).

    History

    Although in the past many Frenchmen liked to refer to their descent from Gallic ancestors ("Nos ancêtres les gaulois"), very little Celtic influence seems to remain in the French of today. Most of the vocabulary is of Latin and Germanic (Frankish) origin.

    Originally, many dialects and languages were spoken throughout contemporary French territory (among them were several langue d'Oïl dialects, like Picard, Valon, etc.), Occitan dialects (Gascon, Provençal, etc.), Breton, Basque, Catalan, Low German, etc., but over time the dialect of the Ile-de-France (the region around Paris), Francien, has supplanted the others and has become the basis for the official French language. The earliest text in French is the Oath of Strasbourg from 842; the period of the language up to around 1300 is called Old French, which after 1300 turned into Middle French, and ultimately, Modern French. Old French became a literary language with the chansons de geste that told tales of the paladins of Charlemagne and the heroes of the Crusades. By the Ordinance of Villers-Cotterêts, in 1539 King Francis I made French the official language of administration and court proceedings in France, ousting the Latin that had been used before then.

    The worldwide use of French

    French is an official language in the following countries:
    country native speakers population pop. dens. area
      (rough est.) (July 2003 est.) (/km²) (km²)
    France (Metropolitan)
    		60,000,000 60,180,600 105 547,030
    Democratic Republic of the Congo 55,225,478 24 2,345,410
    Canada 6,700,000 32,207,000 3 9,976,140
    Madagascar 16,979,900 - 587,040
    Côte d'Ivoire 16,962,500 - 322,460
    Cameroon 15,746,200 - 422,277
    Burkina Faso 13,228,500 - 274,200
    Mali 11,626,300 - 1,240,000
    Senegal 10,580,400 - 196,190
    Belgium 4,000,000 10,290,000 - 30,510
    Rwanda 7,810,100 - 26,338
    Haiti 7,527,800 - 27,750
    Switzerland (millions) 7,318,638 - 41,290
    Burundi 6,096,156 - 27,830
    Togo 5,429,300 - 56,785
    Central African Republic 3,683,600 - 622,984
    Republic of the Congo 2,954,300 - 342,000
    Gabon 1,321,500 - 267,667
    Comoros 632,948 - 2,170
    Djibouti 457,130

    		- 23,000
    Luxembourg 454,157 - 2,586
    Guadeloupe 442,200 - 1,780
    Martinique 390,200 - 1,100
    Vanuatu 200,000 - 12,200
    Seychelles 80,469 - 455

    Although not official, French is the major second language in the following countries.
    country population pop. dens. area
      (July 2003 est.) (/km²) (km²)

    Algeria 32,810,500 - 2,381,440
    Tunisia 9,924,800 - 163,610
    Mauritius 1,210,500 - 2,040
    Morocco 31,689,600 - 446,550

    Also, there are some French-speakers in Egypt, India (Pondicherry), Italy (Aosta Valley), Laos, Mauritania, United Kingdom (Channel Islands), United States of America (mainly Louisiana & New England) and Vietnam.

    La Francophonie is an international organization of French-speaking countries and governments.

    Historically, for nearly 300 years French was also the language of the ruling classes and commerce in England, from the time of the Norman Conquest until 1362, when the use of English was resumed.

    French Phonemes

    French spelling is by no means phonetic. Terminal consonants have often become silent in most dialects, unless followed by a vowel sound (liaison) or silent altogether (e.g., "et" is never pronounced with the ending "t"). In many words, the "n" and "m" become silent and cause the preceding vowel to become nasalized (i.e. pronounced with the soft palate extended downward so as to cause the air to leave through the nostrils instead of through the mouth). Furthermore, French words tend to run together when spoken, with ending consonants often being chained to the start of the next word.

    Rounded

    i y u

    e 2 o

    E 9 O

    a A

    E~9~o~

     ã

    Note: /A/ is for many speakers no longer a phoneme. Whether /@/ (Schwa) is a phoneme of French is controversial. Some see it as an allophone of /9/

    Plosives

    /p, b/

    /k, g/

    /t, d/

    Fricatives

    /s, z/

    /f, v/

    /S, Z/

    Nasals

    /m, n, n_j/ For some speakers, /n_j/ is probably /n/ + /j/

    Lateral

    /l/

    Vibrant

    /r/ (Uvular trill)

    Semi-vowel

    /j/

    Some common phrases

    See also:

    Grammar

    The verb

    There are three main verb categories, verbs ending in -er, -ir and -re.

    French verbs are commonly conjugated in five simple tenses and five compound tenses. They are also conjugated in the "literary" or "historic" tenses, each of which have a commonly used equivalent tense. These literary tenses are used often in literature and history. There are two simple literary tenses and three compound literary tenses.

    The commonly used simple tenses are: the present tense (le présent), the imperfect (l'imparfait), the future (le futur), the present subjunctive (le subjonctif) and the present conditional (le conditionnel).

    The commonly conjugated compound tenses are the perfect (le passé composé), the pluperfect (le plus-que-parfait), the future perfect (le futur antérieur), the imperfect subjunctive (le subjonctif passé) and the past conditional (le conditionnel passé).

    The perfect is the tense in common use used to describe actions that were started and completed in the past. The imperfect is the tense used to describe actions that were ongoing or continuous in the past or to describe habitual or repetitive action. The present and past subjunctives are used to describe doubt, emotions, possibilities and events which may or may not occur.

    The simple literary tenses are the simple past or past historic (le passé simple), replaced in ordinary language by the perfect tense, and the imperfect subjunctive (l'imparfait du subjonctif), replaced in ordinary language by the present subjunctive.

    The compound literary tenses are the past anterior (le passé antérieur), usually replaced by the pluperfect; the pluperfect subjunctive (le plus-que-parfait du subjonctif), usually replaced by the past subjunctive; and a second form of the past conditional.

    Of the literary tenses, only the past historic tends to be used commonly any more. While grammatical distinctions were lost when the literary tenses fell out of common usage, the distinctions were not important enough for confusion to result.

    Aside from these tenses, there is an imperative, a participle, and the infinitive, each of which can be inflected for tense (present and past), although the past imperative is quite rare.

    Compound tense auxiliary verbs

    In French, all compound tenses are formed with an auxiliary verb (either être "to be" or avoir "to have"). Most verbs use avoir as their auxiliary verb. The exceptions are sixteen commonly used verbs of motion and all reflexive verbs.

    The distinction between the two auxiliary verbs is important for the correct formation of the compound tenses and is also essential to the agreement of the past participle.

    The past participle

    The past participle is used in French as both an adjective and to form all the compound tenses of the language. When it is used as an adjective, it follows all the regular agreement rules of the language, but when it is used in compound tenses, it follows special agreement rules.

    -er verbs form the participle by changing the -er ending to -é, -ir verbs by changing -ir to -i, and -re verbs by changing to -u. Therefore, the past participle of parler, "to speak", is parlé; for finir, "to finish", fini, and for vendre, "to sell", vendu.

    The rules of agreement for past participles differ for avoir verbs and être verbs (see "Compound tense auxiliary verbs"). For avoir verbs, the past participle does not agree with the subject unless the direct object comes before the verb, either in the form of a pronoun or a relative clause using que.

    For the sixteen commonly used être verbs, the past participle always agrees with the subject. For reflexive verbs, the past participle generally agrees with the subject, unless there is a direct object to the reflexive verb.

    Legal issues

    France

    France mandates the use of French in official government publications, education (though these dispositions are often ignored) and legal contracts; avertisements must bear a translation of foreign words. Contrary to a myth common in the American and British media, France does not prohibit the use of foreign words in Web pages or any other private publication, which would anyway contradict constitutional guarantees on freedom of speech.

    Canada

    French is one of Canada's two official languages, with English; various provisions of the Canadian Charter of Rights and Freedoms deal with the right of Canadians to access services in French. By law, the federal government must operate and provide services in both English and French; proceedings of the Parliament of Canada must be translated into both English and French; and all Canadian products must be labelled in both English and French.

    French is an official language of New Brunswick, the Northwest Territories, and Nunavut, and is the sole official language of Quebec. The Quebec government enforces certain laws regarding the status of French in the province, including requirements for the use of French in businesses of a certain size; precedence of French-language outdoor signs over English-language ones in commercial settings; and requirements for French-language education for children. Policy regarding the French language in Quebec is the department of the Office québécois de la langue française.

    Varieties of French

    Languages derived from French

    External links

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    List of airports: F

    (From Wikipedia, the free Encyclopedia)

    List of airports: A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

    F

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    List of Biblical names starting with F

    (From Wikipedia, the free Encyclopedia)

    List of Biblical names
    A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - Y - Z

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    List of books by title: F

    (From Wikipedia, the free Encyclopedia)

    List of books in alphabetical order by title:

    A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

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    List of cities in Germany starting with F

    (From Wikipedia, the free Encyclopedia)

    List of cities in Germany: A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

    TownPopulationDistrictBundesland
    Falkenberg/Elster6,500Elbe-ElserBrandenburg
    Fallingbostel11,800Soltau-FallingbostelLower Saxony
    Fellbach42,822Rems-MurrBaden-Württemberg
    Flensburg85,000--Schleswig-Holstein
    Frankenthal48,800--Rhineland-Palatinate
    Frankfurt (Main)643,500--Hesse
    Frankfurt (Oder)77,900--Brandenburg
    Frechen47,000ErftkreisNorth Rhine-Westphalia
    Freiburg200,000--Baden-Württemberg
    Freudenberg18,300Siegen-WittgensteinNorth Rhine-Westphalia
    Friedberg29,100Aichach-FriedbergBavaria
    Fröndenberg23,000UnnaNorth Rhine-Westphalia
    Fürth109,500--Bavaria

    A "--" in the district column means, that the town is a district-free town, i.e. it is by itself a district.

    Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "List of cities in Germany starting with F."

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    List of colleges and universities starting with F

    (From Wikipedia, the free Encyclopedia)

    A -- B -- C -- D -- E -- F -- G -- H -- I -- J -- K -- L -- M -- N -- O -- P -- Q -- R -- S -- T -- U -- V -- W -- X -- Y -- Z
    1. Fachhochschule Fulda
    2. Fachhochschule Furtwangen
    3. Fachhochschule Gießen-Friedberg
    4. Fachhochschule Harz
    5. Fachhochschule Koln
    6. Fachhochschule Karlsruhe
    7. Fachhochschule Konstanz
    8. Fachhochschule Munchen
    9. Fachhochschule Offenburg
    10. Fachhochschule Osnabruck
    11. Fachhochschule Reutlingen, Hochschule fur Technik und Wirtschaft
    12. Faculte Polytechnique de Mons
    13. Fairhaven College
    14. Fairleigh Dickinson University
    15. Fairmont State College
    16. Fanshawe College of Applied Arts and Technology
    17. Fayetteville State University
    18. Federal University of Paraiba
    19. Felician College
    20. Feng Chia University
    21. Ferris State University
    22. Fielding Institute
    23. Fife College of Further and Higher Education
    24. Findhorn College
    25. Fisk University
    26. Fitchburg State College
    27. Flinders University
    28. Florida AandM University
    29. Florida Atlantic University
    30. Florida College
    31. Florida Community College at Jacksonville
    32. Florida Gulf Coast University
    33. Florida Institute of Technology
    34. Florida International University
    35. Florida State University
    36. Fond du Lac Tribal and Community College
    37. Fontbonne College
    38. Foothill College
    39. Fordham University
    40. Fort Belknap College
    41. Fort Hays State University
    42. Fort Lewis College
    43. Foshan University
    44. Fox Valley Technical College
    45. Francis Marion University
    46. Franciscan University of Steubenville
    47. Franco-Polish School of New Information and Communication Technologies
    48. Frankfurt University
    49. Franklin and Marshall College
    50. Franklin College Switzerland
    51. Franklin College, Indiana
    52. Franklin Pierce College
    53. Franklin Pierce Law Center
    54. Franklin W. Olin College of Engineering
    55. Fredonia State University
    56. Freed-Hardeman University
    57. Freie Universitat Berlin
    58. French Naval Academy
    59. Fresno Pacific College
    60. Fridericiana
    61. Friedrich Schiller Universitat, Jena
    62. Friends International Christian University
    63. Friends University
    64. Front Range Community College
    65. Frostburg State University
    66. Fu Jen Catholic University
    67. Fudan University
    68. Fujita Health University
    69. Fukui University
    70. Fukuoka Institute of Technology
    71. Fukuoka Junior College of Technology
    72. Fukushima Medical College
    73. Fukushima University
    74. Fullerton College
    75. Furman University

    See also : Colleges and universities

    Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "List of colleges and universities starting with F."

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    List of Japanese authors:F

    (From Wikipedia, the free Encyclopedia)

    List of Japanese authors

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    List of people by name: F

    (From Wikipedia, the free Encyclopedia)

    List of people by name: A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z Fa-Fd - Fe - Ff - Fg - Fh - Fi - Fj - Fk - Fl - Fm - Fn - Fo - Fp - Fq - Fr - Fs - Ft - Fu-Fz

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    List of people by name: Fa-Fd

    (From Wikipedia, the free Encyclopedia)

    List of people by name: A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z Fa-Fd - Fe - Ff - Fg - Fh - Fi - Fj - Fk - Fl - Fm - Fn - Fo - Fp - Fq - Fr - Fs - Ft - Fu-Fz

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    List of people by name: Fe

    (From Wikipedia, the free Encyclopedia)

    List of people by name: A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z Fa - Fb - Fc - Fd - Fe - Ff - Fg - Fh - Fi - Fj - Fk - Fl - Fm - Fn - Fo - Fp - Fq - Fr - Fs - Ft - Fu - Fv - Fw - Fx - Fy - Fz

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    List of people by name: Fi

    (From Wikipedia, the free Encyclopedia)

    List of people by name: A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z Fa - Fb - Fc - Fd - Fe - Ff - Fg - Fh - Fi - Fj - Fk - Fl - Fm - Fn - Fo - Fp - Fq - Fr - Fs - Ft - Fu - Fv - Fw - Fx - Fy - Fz

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    List of people by name: Fl

    (From Wikipedia, the free Encyclopedia)

    List of people by name: A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z Fa - Fb - Fc - Fd - Fe - Ff - Fg - Fh - Fi - Fj - Fk - Fl - Fm - Fn - Fo - Fp - Fq - Fr - Fs - Ft - Fu - Fv - Fw - Fx - Fy - Fz