*[[ phYsicSsS a Fairytale To Happen?!!?! ]]*

8/12/07

conCave aNd c0nVex MirroRzz...

Concave and Convex Mirrors

The two types of spherical mirrors are shown in the
diagram on the right.

Spherical mirrors can be thought of as a portion of a sphere which was sliced away and then silvered on one of the sides to form a reflecting surface. Concave mirrors were silvered on the inside of the sphere and convex mirrors were silvered on the outside of the sphere.

If a concave mirror is thought of as being a slice of a sphere, then there would be a line passing through the center of the sphere and attaching to the mirror in the exact center of the mirror. This line is known as the principal axis. The point in the center of sphere from which the mirror was sliced is known as the center of curvature and is denoted by the letter C in the diagram below. The point on the mirror's surface where the principal axis meets the mirror is known as the vertex and is denoted by the letter A in the diagram below. The vertex is the geometric center of the mirror. Midway between the vertex and the center of curvature is a point known as the focal point; the focal point is denoted by the letter F in the diagram below. The distance from the vertex to the center of curvature is known as the radius of curvature (abbreviated by "R"). The radius of curvature is the radius of the sphere from which the mirror was cut. Finally, the distance from the mirror to the focal point is known as the focal length (abbreviated by "f"). Since the focal point is the midpoint of the line segment adjoining the vertex and the center of curvature, the focal length would be one-half the radius of curvature.

*[[ And they lived happily ever after... ]]*
|8/12/2007|

fiBer 0pTicS....

What is Fiber Optics

- A means of sending information in the form of light pulses
- Optical fibers are thin strands of glass or plastic that carry these light pulses
- Light pulses are modulated to a optical signal and processed as an electrical signal
- Two strands required, one each to send and receive the signal

The telecommunications industry has placed a great deal of mysteryaround fiber optic signal transmission, but fiber is really quite simplewhen you break it down to the basics.
Fiber Optic signal transmission is simply a way of sending information inthe form of light. Much like Morse Code, pulses of light are transmittedand received and translated into pieces of information. The light is sentthrough strands of glass or plastic, thinner than the diameter of ahuman hair.Electrical current carrying data is converted to light pulses, sent throughthe strand of glass, then converted back to electrical current at thereceiving end of the cable.As light can only travel in one direction at a time, two strands of cableare required one each to send and receive signals.
Transmitters and Receivers are located at each end of the fiber cable.These devices transmit information and receives information in the formof light pulses, which has been converted from electrical current.Very often the transmitter and receiver is in the same component,they're referred to as 'transceivers'.

History

The light-guiding principle behind optical fibers was first demonstrated in by Daniel Colladon and Jaques Babinet in the 1840s, with Irish inventor John Tyndall offering public displays using water-fountains ten years later.[1] Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth century. Image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. The principle was first used for internal medical examinations by Heinrich Lamm in the following decade. In 1952 physicist Narinder Singh Kapany conducted experiments that led to the invention of optical fiber, based on Tyndall's earlier studies; modern optical fibers, where the glass fiber is coated with a transparent cladding to offer a more suitable refractive index, appeared later in the decade.[1] Development then focused on the development of fiber bundles for image transmission. The first fiber optic semi-flexible gastroscope was patented by Basil Hirschowitz, C. Wilbur Peters, and Lawrence E. Curtiss, researchers at the University of Michigan, in 1956. In the process of developing the gastroscope, Curtiss produced the first glass-clad fibers; previous optical fibers had relied on air or impractical oils and waxes as the low-index cladding material. A variety of other image transmission applications soon followed. Optical fibers became practical for use in communications in the late 1970s, once the attenuation was reduced sufficiently; since then, several technical advances have been made to improve the attenuation and dispersion properties of optical fibers (i.e., allowing signals to travel farther and carry more information), and lower the cost of fiber communications systems.
In 1965, Charles K. Kao and George A. Hockham of the British company Standard Telephones and Cables were the first to suggest that attenuation of contemporary fibers was caused by impurities, which could be removed, rather than fundamental physical effects such as scattering. They speculated that optical fiber could be a practical medium for communication, if the attenuation could be reduced below 20 dB per kilometer (Hecht, 1999, p. 114).This attenuation level was first achieved in 1970, by researchers Robert D. Maurer, Donald Keck, Peter C. Schultz, and Frank Zimar working for American glass maker Corning Glass Works, now Corning Inc. They demonstrated a fiber with 17 dB optic attenuation per kilometer by doping silica glass with titanium. A few years later they produced a fiber with only 4 db/km using germanium oxide as the core dopant. Such low attenuations ushered in optical fiber telecommunications and enabled the Internet.
The erbium-doped fiber amplifier, which reduced the cost of long-distance fiber systems by reducing or even in many cases eliminating the need for optical-electrical-optical repeaters, was invented by David Payne of the University of Southampton, and Emmanuel Desurvire at Bell Laboratories in 1986. The two pioneers were awarded the Benjamin Franklin Medal in Engineering in 1998.
In 1991, the emerging field of photonic crystals led to the development of photonic crystal fiber (Science (2003), vol 299, page 358), which guides light by means of diffraction from a periodic structure, rather than total internal reflection. The first photonic crystal fibers became commercially available in 1996 . Photonic crystal fibers can be designed to carry higher power than conventional fiber, and their wavelength dependent properties can be manipulated to improve their performance in certain applications.

*[[ And they lived happily ever after... ]]*
|8/12/2007|

8/5/07

i haTe thiS thing

Having sore eyes is such a stupid thing .What the hell!!! I missed my lessons…. The periodic test is due NEXT WEEK. Wish that I will recover easily……( salamat sa mga taong nag-alala sa akin!!!)