SCIENTISTS
1. He is a great mathematician and physicist who gave - The theory of Relativity. He introduced the famous equation E=m*c*c in the world. He showed energy [E] and matter [M] can be changed from one to the other.
2. He is one of the few scientists in history to understand the importance of conducting experiments. He discovered 8 different gases [INCLUDING OXYGEN] more than any other scientist in history. It was he who discovered that RUBBER CAN BE USED TO ERASE PENCIL MARKS.
His name is JOSEPH PRIESTLY.
3. He is a polish astronomer who believed that the earth and other planets revolve around a stationary sun. This idea totally contradicted the belief of the time that said that all the planets circled in the orbits around the earth. All his astronomical observations were undertaken without the use of a telescope. The telescope was invented in about 1608 which was 65 years after he died.
This great scientist was NICOLAS COPERNICUS.
ELECTRONIC WASTE ( E- WASTE)
many believe that environmental dangers of used electronics have been exaggerated.
agency includes discarded CRT monitors in its category of "hazardous household waste" but considers CRTs that have been set aside for testing to be commodities if they are not discarded, speculatively accumulated or left unprotected from weather and other damage.
Rapid changes in technology, changes in media, falling prices and planned obsolescence have resulted in a fast-growing surplus of electronic waste around the globe. Dave Kruch, CEO of Cash For Laptops, regards electronic waste as a "rapidly expanding" issue. Technical solutions are available, but in most cases a legal framework, a collection system, logistics, and other services need to be implemented before a technical solution can be applied. Display units, Processors, and audio components have different useful lives. Processors are most frequently outdated and are more likely to become "e-waste", while display units are most often replaced while working without repair attempts, due to changes in display technology.
An estimated 50 million tons of E-waste is produced each year. The USA discards 30 million computers each year and 100 million phones are disposed of in Europe each year. The Environmental Protection Agency estimates that only 15-20% of e-waste is recycled, the rest of these electronics go directly into landfills and incinerators."EPA estimates for 2006-07".According to a report by UNEP titled, "Recycling - from E-Waste to Resources," the amount of e-waste being produced - including mobile phones and computers - could rise by as much as 500 percent over the next decade in some countries. The United States is the world leader in producing electronic waste, tossing away about 3 million tons each year. China already produces about 2.3 million tons domestically, second only to the United States. Despite having banned e-waste imports, China remains a major e-waste dumping ground for developed countries.
ELECTRICAL BATTERY
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta, batteries have become a common power source for many household and industrial applications. According to a 2005 estimate, the worldwide battery industry generates $48 billion in sales each year with 6% annual growth. There are two types of batteries: primary batteries, which are designed to be used once and discarded and secondary batteries which are designed to be recharged and used multiple times. Batteries come in many sizes, from miniature cells used to power hearing aids and wristwatches to battery banks the size of rooms that provide standby power for telephone exchanges and computer data centers.
Strictly, a battery is a collection of multiple electrochemical cells, but in popular usage battery often refers to a single cell. For example, a 1.5-volt battery is a single 1.5-volt cell and a 9-volt battery has six 1.5-volt cells in series. The first electrochemical cell was developed by the Italian physicist Alessandro Volta in 1792 and in 1800 he invented the first battery, a "pile" of many cells in series. The usage of "battery" to describe electrical devices dates to Benjamin Franklin, who in 1748 described multiple Leyden jars by analogy to a battery of cannons. Thus Franklin's usage to describe multiple Leyden jars predated Volta's use of multiple galvanic cells. It is speculated but not established, that several ancient artifacts consisting of copper sheets and iron bars and known as Baghdad batteries may have been galvanic cells. Volta's work was stimulated by the Italian anatomist and physiologist Luigi Galvani, who in 1780 noticed that dissected frog's legs would twitch when struck by a spark from a Leyden jar, an external source of electricity. In 1786 he noticed that twitching would occur during lightning storms. After many years Galvani learned how to produce twitching without using any external source of electricity. In 1791 he published a report on "animal electricity."He created an electric circuit consisting of the frog's leg and two different metals A and B, each metal touching the frog's leg and each other. In modern terms, the frog's leg served as both the electrolyte and the sensor and the metals served as electrodes. He noticed that even though the frog was dead, its legs would twitch when he touched them with the metals. Within a year, Volta realized the frog's moist tissues could be replaced by cardboard soaked in salt water and the frog's muscular response could be replaced by another form of electrical detection.
THE MAGLEV (SUPER CONDUCTIVE MAGNETIC RAILS)
Maglev (magnetic rails) is a system of transportation that uses magnetic levitation to suspend, guide and propel vehicles from magnets rather than using mechanical methods, such as friction-reliant wheels, axles and bearings. Maglevs are not mechanical rail technology. Maglev transport is a means of flying a vehicle or object along a guideway by using magnets to create both lift and thrust, albeit only a few inches above the guideway surface. High-speed maglev vehicles are lifted off their guideway and thus move more smoothly, quietly and require less maintenance than wheeled mass transit systems - regardless of speed. This non-reliance on friction also means that acceleration and deceleration can far surpass that of existing forms of transport. The power needed for levitation is not a particularly large percentage of the overall energy consumption. Most of the power used is needed to overcome air resistance, as with any other high speed form of transport.
The highest recorded speed of a Maglev train is 581 km/h, achieved in Japan by the CJR's MLX01 superconducting maglev in 2003, 6 km/h faster than the conventional TGV wheel-rail speed record. However, the operational and performance differences between these two very different technologies is far greater than a 6 km/h of speed. For example, the TGV record was achieved accelerating down a 72 km slight incline, requiring 13 minutes. It then took another 77 km for the TGV to stop, requiring a total distance of 149 km for the test. The MLX01 record however, was achieved on the 18.4 km Yamanashi test track - 1/8 the distance needed for the TGV test. While it is claimed high-speed maglevs can actually operate commercially at these speeds while wheel-rail trains cannot and do so without the burden and expense of extensive maintenance, no maglev or wheel-rail commercial operation has actually been attempted at these speeds
over 500 kph. Differences in construction costs can affect chances for profitability.
LASER
The word laser started as an acronym for "light amplification by stimulated emission of radiation". In modern usage "light" broadly denotes electromagnetic radiation of any frequency, not only visible light, hence infrared laser, ultraviolet laser, X-ray laser, and so on. Because the microwave predecessor of the laser, the maser, was developed first, devices of this sort operating at microwave and radio frequencies are referred to as "masers" rather than "microwave lasers" or "radio lasers". In the early technical literature, especially at Bell Telephone Laboratories, the laser was called an optical maser; this term is now obsolete.
A laser which produces light by itself is technically an optical oscillator rather than an optical amplifier as suggested by the acronym. It has been humorously noted that the acronym LOSER, for "light oscillation by stimulated emission of radiation," would have been more correct. With the widespread use of the original acronym as a common noun, actual optical amplifiers have come to be referred to as "laser amplifiers", notwithstanding the apparent redundancy in that designation.
The back-formed verb to lase is frequently used in the field, meaning "to produce laser light", especially in reference to the gain medium of a laser, when a laser is operating it is said to be "lasing". Further use of the words laser and maser in an extended sense, not referring to laser technology or devices, can be seen in usages such as astrophysical maser and atom laser.
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation. The emitted laser light is notable for its high degree of spatial and temporal coherence, unattainable using other technologies.
Spatial coherence typically is expressed through the output being a narrow beam which is diffraction-limited, often a so-called "pencil beam." Laser beams can be focused to very tiny spots, achieving a very high irradiance. Or they can be launched into a beam of very low divergence in order to concentrate their power at a large distance.
Temporal coherence implies a polarized wave at a single frequency whose phase is correlated over a relatively large distance along the beam. A beam produced by a thermal or other incoherent light source has an instantaneous amplitude and phase which vary randomly with respect to time and position, and thus a very short coherence length.
Most so-called "single wavelength" lasers actually produce radiation in several modes having slightly different frequencies often not in a single polarization. And although temporal coherence implies monochromaticity, there are even lasers that emit a broad spectrum of light, or emit different wavelengths of light simultaneously. There are some lasers which are not single spatial mode and consequently their light beams diverge more than required by the diffraction limit. However all such devices are classified as "lasers" based on their method of producing that light: stimulated emission. Lasers are employed in applications where light of the required spatial or temporal coherence could not be produced using simpler technologies.
The gain medium of a laser is a material of controlled purity, size, concentration, and shape, which amplifies the beam by the process of stimulated emission. It can be of any state: gas, liquid, solid or plasma. The gain medium absorbs pump energy, which raises some electrons into higher-energy quantum states. Particles can interact with light by either absorbing or emitting photons. Emission can be spontaneous or stimulated. In the latter case, the photon is emitted in the same direction as the light that is passing by. When the number of particles in one excited state exceeds the number of particles in some lower-energy state, population inversion is achieved and the amount of stimulated emission due to light that passes through is larger than the amount of absorption. Hence, the light is amplified. By itself, this makes an optical amplifier. When an optical amplifier is placed inside a resonant optical cavity, one obtains a laser.
The light generated by stimulated emission is very similar to the input signal in terms of wavelength, phase, and polarization. This gives laser light its characteristic coherence, and allows it to maintain the uniform polarization and often monochromaticity established by the optical cavity design.
The optical resonator is sometimes referred to as an "optical cavity", but this is a misnomer: lasers use open resonators as opposed to the literal cavity that would be employed at microwave frequencies in a maser. The resonator typically consists of two mirrors between which a coherent beam of light travels in both directions, reflecting back on itself so that an average photon will pass through the gain medium repeatedly before it is emitted from the output aperture or lost to diffraction or absorption. If the amplification in the medium is larger than the resonator losses, then the power of the recirculating light can rise exponentially. But each stimulated emission event returns an atom from its excited state to the ground state, reducing the gain of the medium. With increasing beam power the net gain reduces to unity and the gain medium is said to be saturated. In a continuous wave laser, the balance of pump power against gain saturation and cavity losses produces an
equilibrium value of the laser power inside the cavity. This equilibrium determines the operating point of the laser. If the applied pump power is too small, the gain will never be sufficient to overcome the resonator losses, and laser light will not be produced. The minimum pump power needed to begin laser action is called the lasing threshold. The gain medium will amplify any photons passing through it, regardless of direction but only the photons in a spatial mode supported by the resonator will pass more than once through the medium and receive substantial amplification.
The beam in the cavity and the output beam of the laser, when travelling in free space rather than waveguides, can be approximated as a Gaussian beam in most lasers, such beams exhibit the minimum divergence for a given diameter. However some high power lasers may be multimode, with the transverse modes often approximated using Hermite-Gaussian functions. It has been shown that unstable laser resonators produce fractal shaped beams. Near the beam "waist", it is highly collimated: the wavefronts are planar, normal to the direction of propagation, with no beam divergence at that point. However due to diffraction, that can only remain true well within the Rayleigh range. The beam of a single transverse mode laser eventually diverges at an angle which varies inversely with the beam diameter, as required by diffraction theory. The "pencil beam" directly generated by a
common helium-neon laser would spread out to a size of perhaps 500 kilometers when shone on the Moon. On the other hand the light from a semiconductor laser typically exits the tiny crystal with a large divergence up to 50°. However even such a divergent beam can be transformed into a similarly collimated beam by means of a lens system, as is always included, for instance, in a laser pointer whose light originates from a laser diode. That is possible due to the light being of a single spatial mode. This unique property of laser light, spatial coherence, cannot be replicated using standard light sources as can be appreciated by comparing the beam from a flashlight to that of almost any laser.
The mechanism of producing radiation in a laser relies on stimulated emission, where energy is extracted from a transition in an atom or molecule. This is a quantum phenomenon discovered by Einstein who derived the relationship between the A coefficient describing spontaneous emission and the B coefficient which applies to absorption and stimulated emission. However in the case of the free electron laser, atomic energy levels are not involved. It appears that the operation of this rather exotic device can be explained without reference to quantum mechanics.
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