BIGGEST WATERFALL IN THE WORLD- GUAIRA FALLS,BRAZIL

BIGGEST WATERFALL IN THE WORLD- GUAIRA FALLS,BRAZIL

Guaíra Falls were a series of immense waterfalls on the Paraná River along the border between Brazil and Paraguay. The falls no longer exist, inundated in 1982 by the impoundment of the Itaipu Dam reservoir. While published figures vary, ranging from 470,000 cubic feet (13,000 m³) per second to 1,750,000 cubic feet (50,000 m³) per second, Guaíra's flow rate was among the greatest of any then-existing falls on Earth.

The falls comprised 18 cataracts clustered in seven groups—hence their Portuguese name, Sete Quedas (Seven Falls)—near the Brazilian municipality of Guaíra, Paraná and Salto de Guairá, the easternmost city in Paraguay. The falls were located at a point where the Paraná River was forced through a narrow gorge. At the head of the falls, the river narrowed sharply from a width of about 1,250 feet (380 m) to 200 feet (61 m). The total height of the falls was approximately 375 feet (114 m), while the largest individual cataract was 130 feet (40 m) high. The roar of the plunging water could be heard from 20 miles (32 km) away.

Light scattering - Science.

Light scattering is a form of scattering in which light is the form of propagating energy which is scattered. Light scattering can be thought of as the deflection of a ray from a straight path, for example by irregularities in the propagation medium,particles, or in the interface between two media. Deviations from the law of reflection due to irregularities on a surface are also usually considered to be a form of scattering. When these irregularities are considered to be random and dense enough that their individual effects average out, this kind of scattered reflection is commonly referred to as diffuse reflection.

Most objects that one sees are visible due to light scattering from their surfaces. Indeed, this is our primary mechanism of physical observation. Scattering of light depends on the wavelength or frequency of the light being scattered. Since visible light has wavelength on the order of a micro metre, objects much smaller than this cannot be seen, even with the aid of a microscope. Colloidal particles as small as 1 µm have been observed directly in aqueous suspension.

The transmission of various frequencies of light is essential for applications ranging from window glass to fiber optic transmission cables and infrared (IR) heat-seeking missile detection systems. Light propagating through an optical system can be attenuated by absorption, reflection and scattering.

TYPE OF SCATTERING

• Rayleigh scattering is the elastic scattering of light by molecules and particulate matter much smaller than the wavelength of the incident light. It occurs when light penetrates gaseous, liquid, or solid phases of matter. Rayleigh scattering intensity has a very strong dependence on the size of the particles (it is proportional the sixth power of their diameter). It is inversely proportional to the fourth power of the wavelength of light, which means that the shorter wavelength in visible light (violet and blue) are scattered stronger than the longer wavelengths toward the red end of the visible spectrum. This type of scattering is therefore responsible for the blue color of the sky during the day.and the orange colors during sunrise and sunset. Rayleigh scattering is the main cause of signal loss in optical fibers.

• Mie scattering is a broad class of scattering of light by spherical particles of any diameter. The scattering intensity is generally not strongly dependent on the wavelength, but is sensitive to the particle size. Mie scattering coincides with Rayleigh scattering in the special case where the diameter of the particles is much smaller than the wavelength of the light; in this limit, however, the shape of the particles no longer matters. Mie scattering intensity for large particles is proportional to the square of the particle diameter.

• Tyndall scattering is similar to Mie scattering without the restriction to spherical geometry of the particles. It is particularly applicable to colloidal mixtures and suspensions.

• Brillouin scattering occurs from the interaction of photons with acoustic phonons in solids, which are vibrational quanta of lattice vibrations, or with elastic waves in liquids. The scattering is inelastic, meaning it is shifted in energy from the Rayleigh line frequency by an amount that corresponds to the energy of the elastic wave or phonon, and it occurs on the higher and lower energy side of the Rayleigh line, which may be associated with the creation and annihilation of a phonon.The light wave is considered to be scattered by the density maximum or amplitude of the acoustic phonon, in the same manner that X-rays are scattered by the crystal planes in a solid. In solids, the role of the crystal planes in this process is analogous to the planes of the sound waves or density fluctuations. Brillouin scattering measurements require the use of a high-contrast Fabry–Pérot interferometer to resolve the Brillouin lines from the elastic scattering, because the energy shifts are very small (< 100 cm⁻¹) and very weak in intensity. Brillouin scattering measurements yield the sound velocities in a material, which may be used to calculate the elastic constants of the sample.

• Raman scattering is another form of inelastic light scattering, but instead of scattering from acoustic phonons, as in Brillouin scattering, the light interacts with optical phonons, which are predominantly intra-molecular vibrations and rotations with energies larger than acoustic phonons. Raman scattering may therefore be used to determine chemical composition and molecular structure.Since most Raman lines are stronger than Brillouin lines, and have higher energies, standard spectrometers using scanning monochromators may be used to measure them. Raman spectrometers are standard equipment in many chemical laboratories.

World Wide Web

Many people use the terms Internet and World Wide Web, or just the Web, interchangeably, but the two terms are not synonymous. The World Wide Web is only one of hundreds of services used on the Internet. The Web is a global set of documents, images and other resources, logically interrelated by hyperlinks and referenced with Uniform Resource Identifiers (URIs). URIs symbolically identify services,servers, and other databases, and the documents and resources that they can provide. Hypertext Transfer Protocol (HTTP) is the main access protocol of the World Wide Web. Web services also use HTTP to allow software systems to communicate in order to share and exchange business logic and data.

World Wide Web browser software, such as Microsoft's Internet Explorer, Mozilla Firefox, Opera, Apple's Safari, and Google Chrome, lets users navigate from one web page to another via hyperlinks embedded in the documents. These documents may also contain any combination of computer data, including graphics, sounds, text, video, multimedia and interactive content that runs while the user is interacting with the page. Client-side software can include animations, games, office applications and scientific demonstrations. Through keyword-driven Internet research using search engines like Yahoo! and Google, users worldwide have easy, instant access to a vast and diverse amount of online information. Compared to printed media, books, encyclopedias and traditional libraries, the World Wide Web has enabled the decentralization of information on a large scale.

The Web has also enabled individuals and organizations to publish ideas and information to a potentially large audience online at greatly reduced expense and time delay. Publishing a web page, a blog, or building a website involves little initial cost and many cost-free services are available. Publishing and maintaining large, professional web sites with attractive, diverse and up-to-date information is still a difficult and expensive proposition, however. Many individuals and some companies and groups use web logs or blogs, which are largely used as easily updatable online diaries. Some commercial organizations encourage staff to communicate advice in their areas of specialization in the hope that visitors will be impressed by the expert knowledge and free information, and be attracted to the corporation as a result.

One example of this practice is Microsoft, whose product developers publish their personal blogs in order to pique the public's interest in their work. Collections of personal web pages published by large service providers remain popular, and have become increasingly sophisticated. Whereas operations such as Angelfire and GeoCities have existed since the early days of the Web, newer offerings from, for example, Facebook and Twitter currently have large followings. These operations often brand themselves as social network services rather than simply as web page hosts.

Advertising on popular web pages can be lucrative, and e-commerce or the sale of products and services directly via the Web continues to grow.

When the Web developed in the 1990s, a typical web page was stored in completed form on a web server, formatted in HTML, complete for transmission to a web browser in response to a request. Over time, the process of creating and serving web pages has become dynamic, creating flexible design, layout, and content. Websites are often created using content management software with, initially, very little content. Contributors to these systems, who may be paid staff, members of an organization or the public, fill underlying databases with content using editing pages designed for that purpose, while casual visitors view and read this content in HTML form. There may or may not be editorial, approval and security systems built into the process of taking newly entered content and making it available to the target visitors.

The Hubble Space Telescope - Space telescope

The Hubble Space Telescope (HST) is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation.A 2.4-meter (7.9 ft) aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared spectra. The telescope is named after the astronomer Edwin Hubble.

Hubble's orbit outside the distortion of Earth's atmosphere allows it to take extremely high-resolution images with almost no background light. Hubble's Deep Field has recorded some of the most detailed visible-light images ever, allowing a deep view into space and time. Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.

Although not the first space telescope, Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy. The HST was built by the United States space agency NASA, with contributions from the European Space Agency, and is operated by the Space Telescope Science Institute. The HST is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope.

Space telescopes were proposed as early as 1923. Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the Challenger disaster. When finally launched in 1990, Hubble's main mirror was found to have been ground incorrectly, compromising the telescope's capabilities. The optics were corrected to their intended quality by a servicing mission in 1993.

Hubble is the only telescope designed to be serviced in space by astronauts. Between 1993 and 2002, four Space Shuttle missions repaired, upgraded, and replaced systems on the telescope; a fifth mission was canceled on safety grounds following the Columbia disaster. However, after spirited public discussion, NASA administrator Mike Griffin approved one final servicing mission, completed in 2009. The telescope is now expected to function until at least 2014, and possibly 2020. Its scientific successor, the James Webb Space Telescope (JWST), is currently scheduled to be launched in 2018.