Category Science

How does Recording happen?

RECORDING

 To record sound, the pattern of vibrations in the air must be turned into a form that can be stored. The gramophone was the first sound-recording device. To record, the sound was made to vibrate a needle, which cut a wavy groove in a foil surface. To play back, the needle moved along the groove, making a diaphragm vibrate to reproduce the sound. In the electric gramophone, introduced in the 1920s, the vibrating needle created an electrical signal, which was amplified to drive a loudspeaker.

The first type of gramophone was the phonograph, invented in 1877 by the American inventor Thomas Edison.

Tape recording was developed in the 1940s. To record on to tape, the electrical signal from a microphone is sent to an electromagnet, which creates a pattern in the tiny magnetic particles that coat the tape. This pattern recreates the signal as the tape plays, and the signal is amplified before going to a speaker.

Most sound recording is now done digitally. A microphone turns the sound into an analogue electrical signal, which is then digitized more than 44,000 times a second to create a long string of binary numbers. The binary numbers can be stored in a computer’s memory or disc drives, or on a compact disc (CD). On a CD, the binary digits 0 and 1 are represented by flat areas or shallow pits in the surface. In a CD player, these are detected by a laser as the disc spins and reflected to a light-sensitive device. Electronics rebuild the original electric signal, which is amplified and sent to speakers. Computer CD-ROMs and DVDs work in the same way.

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What is Steam Engine?

STEAM ENGINES

An engine is a machine that converts the energy stored in fuel into energy for operating other machines. In a steam engine, burning fuel heats water in a boiler, turning it to steam, which builds up in the boiler. The pressurized steam is used to operate the moving parts of the engine. In the first century AD, the Greek inventor Hero built a device that was turned by jets of steam, but it was a curiosity rather than a useful machine.

The first steam-powered machine was built in 1698 by English engineer Thomas Savery. It was designed to pump water from flooded mines, but was never actually used. In Savery’s engine, steam from the boiler filled a large cylinder. Then cold water was poured over the outside of the cylinder, which cooled it, making the steam condense (turn back to liquid water).This created a vacuum in the cylinder, which sucked in water from the mine through a pipe. More steam was fed to the cylinder to push the water up an outlet pipe.

Thomas Savery called his steam engine the “miner’s friend”. It pumped water from the pipe at the bottom into the pipe at the top via the two large cylinders.

In Thomas Newcomen’s atmospheric steam engine, movement of the piston was transferred to the pump by a rocking beam.

In 1712 another English engineer, Thomas Newcomen, also completed a steam engine for pumping mine water. In Newcomen’s engine, steam from the boiler went along pipes to a cylinder, where its pressure pushed a piston upwards. Then cold water was sprayed into the cylinder, which made the steam condense. This reduced the pressure in the cylinder, and the pressure of the air in the atmosphere outside pushed the piston back down. This is why Newcomen’s engine is often called an atmospheric engine. Although it used a huge amount of coal, it was very successful, especially at coal mines, where there was an endless supply of coal.

WATT’S IMPROVEMENTS

Steam engine design was greatly improved in the 1770s by Scottish engineer James Watt. He realized that Newcomen’s engine was very inefficient because the cylinder was heated and cooled on every cycle. So Watt built his own engine, which became popular for powering industrial machinery, such as spinning and weaving machines.

Steam engines are still used today in power stations in the form of the steam turbine, where high-pressure steam makes a fan-like turbine spin at high speed.

James Watt’s steam engine included many improvements over Thomas Newcomen’s. It had a separate cylinder where the steam was condensed, allowing the main cylinder to remain hot all the time. The piston was double-acting, which means it was moved both up and down by steam. This was achieved by feeding steam to one side of the piston then the other. An automatic governor controlled the flow of steam to the cylinder, and so regulated its speed. Sun-and-planet gears converted the up-and-down movement of the cylinder into a turning movement.

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What is a Telescope and it’s various types?

TELESCOPES

A telescope is an instrument that makes distant objects appears closer, allowing the viewer to see details that are not visible with the naked eye. Terrestrial telescopes are used for spotting wildlife (binoculars are made up of two telescopes, one for each eye), on gun sights and in periscopes. Astronomical telescopes are used to study objects in space. Terrestrial telescopes and most astronomical telescopes are optical telescopes, which collect light coming from distant objects and use it to produce images of the objects.

Italian scientist Galileo used the first astronomical telescope in 1609, with which he discovered moons around Jupiter.

There are two main types of optical telescope – refracting telescopes and reflecting telescopes. In a refracting telescope, a convex (bulging) lens collects light from the distant object and focuses it to form an image of the object. This image is very small, but is much larger than the image formed in the human eye. In a reflecting telescope, a concave (dish-shaped) mirror collects the light from the object and focuses it to form the image. Larger telescopes are nearly always reflecting telescopes because large mirrors are easier to manufacture than large lenses.

The Keck telescope in Hawaii has a main mirror 10 metres across. It is housed in a special building called an observatory.

The larger the lens of a refracting telescope or the mirror of a reflecting telescope, the brighter the image of the object observed, and the fainter the objects that can be seen with the telescope. The image is viewed with an eyepiece lens, which works like a magnifying glass to make it appear much larger.

RADIO TELESCOPES

Objects in space, such as stars and galaxies, do not just give off light. They also give off radiation from other parts of the electromagnetic spectrum, such as infrared radiation, radio waves, X-rays and ultraviolet radiation. These can show up objects that are otherwise invisible. They cannot be seen with ordinary optical telescopes, so special telescopes are needed.

Radio telescopes have a huge dish that acts as a reflector, collecting radio waves and focusing them on to a detector. Radio astronomy has allowed the discovery of new celestial objects, such as pulsars.

SPACE TELESCOPES

The Earth’s atmosphere stops many types of radiation from reaching the surface. To study these sorts of radiation, space telescopes must be launched into Earth orbit. They need special mirrors to reflect and focus the radiation, and electronic detectors to record the images formed, which are radioed back to Earth. Optical telescopes also benefit from being in orbit because the atmosphere distorts light rays as they pass through it. The Hubble Space Telescope, launched by space shuttle in 1990, is the most complex space telescope so far. It can detect visible light, infrared and ultraviolet rays.

The Hubble Space Telescope can see 10 times more detail than Earth-based telescopes and objects 50 times as faint. Solar panels provide its power. Images are transmitted via antennae.

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What is Laser and it’s major types?

LASERS

A laser is a device that creates an intense beam of light called a laser beam. A laser beam is monochromatic: it is made up of light of just one colour of the spectrum. This means that all the light waves in it have the same wavelength. Just as importantly, all the waves are “in phase”, which means that as they leave the laser, their crests and troughs all line up with each other.

The lasing material is contained in a tube with a mirror at one end and half-silvered mirror at the other. Light bounces up and down, gaining strength until it is powerful enough to break out.

The word “laser” is short for Light Amplification by Stimulated Emission of Radiation. Inside the laser is lasing material, which can be a solid, a liquid or a gas. The atoms of the material are excited or “stimulated” by giving them energy, either in the form of light or electricity. This makes them emit light (a type of radiation), which in turn makes other atoms emit light of the same wavelength. This process creates an intense laser beam. The wavelength and so the colour, of a laser beam depends on the lasing material. Some lasers produce ultraviolet or infrared radiation rather than visible light. The first working laser was built by American physicist Theodore Maiman in 1960.

A high-power laser is being used to perform eye surgery. If the retina, the part of the eye that contains light-sensitive cells, becomes detached, a laser beam can stick it back in place.

USES FOR LASERS

The most common uses of lasers are playing compact discs and reading bar codes. These lasers are normally red lasers that use semiconductor lasing materials. They are low-power lasers, but they are still dangerous to look at directly. Low-power lasers are also used in communications, where they send signals along optical-fibre cables, in laser printers, in surveying, and for light shows. High-power lasers can be focused to create intense heat in materials. They are used in manufacturing for accurate cutting and in medicine for delicate surgery.

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What is Microscopes? Throw some light of Microscopes.

MICROSCOPES

A microscope is an instrument that magnifies very small objects, allowing the viewer to see detail in the object that is invisible to the naked eye. Microscopes are used mostly, but not only, in biology and medical research.

There are two main types of microscope – optical microscopes and electron microscopes. In an optical microscope, the image of the object is created by light. The simplest optical microscope is a magnifying glass, which contains a single lens. The lens gathers and bends light coming from the object, making the object look larger than it really is. Compound microscopes have more than one lens. A standard compound microscope has two groups of lenses. The first group, called the objective, gathers light from the object and focuses it to create a magnified image of the object. The second group, called the eyepiece, magnifies this image.

The first compound microscope was probably built by Dutch spectacle-maker Zacharias Janssen in about 1590. Early microscopes had poor-quality lenses and gave blurred images. In the 1670s another Dutchman, Anton van Leeuwenhoek, began making simple, single-lens microscopes. He was the first person to see microorganisms, such as bacteria and amoebae.

ELECTRON MICROSCOPES

Optical microscopes can only magnify objects up to 2000 times. Greater magnifications do not reveal any more detail. Electron microscopes can magnify objects more than a million times. In an electron microscope, a beam of tiny particles called electrons does the same job as light in an optical microscope. It is fired at the object and then focused by electromagnetic “lenses” on to a screen that emits light where the electrons hit it.

There are two main types of electron microscope. In a transmitting electron microscope (TEM), the beam of electrons is fired through an extremely thin slice of the specimen under investigation. In a scanning electron microscope (SEM), a very narrow beam of electrons is fired at the surface of the specimen. The beam scans across the surface of the specimen and a sensor detects the electrons bouncing off. In this way, a three-dimensional image of the specimen is gradually built up.

The images created by electron microscopes are called electron photomicrographs. They may be viewed on television screens using video cameras, or digitized and viewed on computer screens.

The first electron microscope, which could magnify objects up to 400 times, was built in 1932 by German engineers Ernst Ruska and Max Knoll. The newest type of electron microscope is the scanning tunneling electron microscope (STM). It can magnify up to 100 million times, which is enough to see individual atoms.

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What is the process of Printing?

Printing is the process of making many copies of a document or a picture. Printing is normally done on paper, but it can also be done on fabrics, and sheets of plastic or metal. Books are printed on a machine called a printing press. The text and pictures start as patterns on a plate. In the press, the plate is inked so that these areas become ink-covered, and are pressed on to the paper via a rubber-covered drum. A fast printing press can make several prints a second because each print is made by one simple operation.

One of the first methods of printing was wood-block printing; where the images to be printed were carved in reverse into wooden blocks. The blocks were then inked and pressed onto paper to make a print. Ink from the raised areas was transferred on to the paper. Simple block printing is still used for hand-printed textiles.

In an early printing press a screw was turned to press the paper firmly down on to inked type.

Two of the most important inventions in printing were moveable metal type (which allowed words and paragraphs to be built up from individual metal blocks with letters on them) and the printing press. In Europe, these were both developed in the fifteenth century by the German printing pioneer Johannes Gutenberg. They allowed books to be printed in large quantities, whereas before each book had to be hand-copied.

On a printed colour page, the text is normally solid black ink, while the pictures are made up of tiny dots of coloured – and black – ink.

Most colour printing is done with just four colours of ink: cyan, magenta, yellow and black. By printing dots in varying sizes, the first three colours combine to create almost any other colour. In practice, all three mixes to create brown, so black is used to darken some areas.

In a modern printing press, printing is carried out using a sheet of metal called a printing plate, rather than with individual blocks of type. The shape of the letters that make up the text, together with the dots that make up the pictures, appear as patterns on the surface of the plate. The plates are prepared using photographic and chemical processes.

Type and pictures for a book, magazine or leaflet are nowadays usually designed and laid out on a computer using desktop publishing software. The files from the computer may then be sent to the printer, which uses them to make four printing plates, one for each colour of ink on the printing press.

For most publications, the paper needs to be printed on both sides. Some presses can do this but on others the paper has to be sent through the press twice. Several pages of the final book or magazine are normally printed on each sheet of paper. The sheets then go for print finishing, where machines fold, collate (sort), staple or sew, and trim the sheets to create the finished product.

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