Light and Gravity
Albert Einstein also put forward the idea that light can be bent both by refraction, and by gravity. Light ordinarily travels on a straight line path but it will follow a curved path if it passes through a strong gravitational field. This is called 'curved space,' and this explains why light becomes trapped in a black hole. • Radha Nair
Saturday, December 14, 2013
light:Praxinoscope
Praxinoscope
The praxinoscope was a toy that converted still pictures into moving pictures. It consisted of a Praxinoscope lamp surrounded by a ring of still pictures showing an object in different stages of movement. Each picture faced a mirror. By turning a handle, the ring could be turned fast enough so that the reflections in the mirror would merge, and it would look as though the object was moving.
The praxinoscope was a toy that converted still pictures into moving pictures. It consisted of a Praxinoscope lamp surrounded by a ring of still pictures showing an object in different stages of movement. Each picture faced a mirror. By turning a handle, the ring could be turned fast enough so that the reflections in the mirror would merge, and it would look as though the object was moving.
light:amazing
amazing
Chameleon's Eyes
A Chameleon's eyes have a 360-degree arc of vision. It can rotate each eye independently of the other, and so, can see two directions at once.
Invisible Fish
The hatchet fish found only in the deep sea, has sides that are covered with large silver scales that act like mirrors, and two rows of light-producing organs on its underside. The effect is to make the fish invisible to its enemies.
Ancient Fireworks
Fire was first produced by striking together pieces of either flint or iron pyrites. These minerals give off sparks when they are hit with something hard. Later, flint and iron pyrite were both used to ignite gunpowder in ancient rifles.
Chameleon's Eyes
A Chameleon's eyes have a 360-degree arc of vision. It can rotate each eye independently of the other, and so, can see two directions at once.
Invisible Fish
The hatchet fish found only in the deep sea, has sides that are covered with large silver scales that act like mirrors, and two rows of light-producing organs on its underside. The effect is to make the fish invisible to its enemies.
Ancient Fireworks
Fire was first produced by striking together pieces of either flint or iron pyrites. These minerals give off sparks when they are hit with something hard. Later, flint and iron pyrite were both used to ignite gunpowder in ancient rifles.
light:star fact
star fact
Light to Lead
In ancient times, people made fires at the edge of the water to warn boats of dangerous rocks and shores. Later, light-houses were built to serve this purpose. The first proper lighthouses were built by the pharaohs of Alexandria.
Auroras
The word 'aurora' means 'dawn' in Latin. Auroras are spectacular displays of light seen in the sky over the Polar Regions. They are caused when tiny electrically charged particles from the Sun collide with the atoms in the Earth's atmosphere.
Protection for the Retina
The pupil is a tiny hole in front of the iris that controls the amount of light entering the eye. This is important, because too much light can cause damage to the retina.
Night Vision
People who have to work in the dark often wear night vision goggles. These goggles are designed on the principle that even in pitch darkness, there is some reflected light, which we cannot normally see. Moreover, all objects give off 'heat' energy, which is not visible to the human eye. Night vision goggles are designed to collect and amplify all those tiny bits of available light so that our eyes have enough light to see in the dark. This is called image enhancement technology. The other technology used in night vision equipment is called thermal imaging. It takes advantage of the infrared light given off by objects, which is not visible to human eyes.
Tricky Sunlight
During the day, sunlight looks golden. However, as sunset approaches, the light takes on orange and red hues. This is because the rays become more slanting and have to travel sideways through more layers of air. As this happens, more and more of blue light, which has a shorter wavelength is absorbed and only the colours with longer wavelengths like orange and red are seen.
Improving Vision
For almost 700 years, spectacles have helped people with poor eyesight to see better. Spectacles with convex lenses help people with long sight, to see nearby objects more clearly. concave lenses are used by people with short sight, so that they can see far off objects more clearly.
Contact Lenses
A contact lens is a thin lens that is placed directly on the eye to improve vision. These lenses float on a film of tears in front of the cornea and are today made of plastic or silicon. Like spectacles, they are used to correct a variety of vision problems including myopia and astigmatism.
Why Diamonds Glitter
Diamonds behave like prisms. When light passes through a cut diamond, it is bent into different wavelengths, and the colours separate, and then are reflected back out. Since a diamond's shape is different from a prism's, the colours don't appear in Straight rows, but more like shards of colour as in a kaleidoscope. As a diamond moves, the shards of colours change like in a kaleidoscope, making the diamond glitter.
Galileo's Telescope
Galileo's earliest telescope contained two lenses-a convex lens, and a smaller concave eyepiece lens. Galileo used his telescopes to look at the Moon, the planets, and the stars.
Colourful Communcation
The octopus, cuttlefish, and squid have special cells that are filled with different coloured pigments. The size of these cells can be controlled by the brain. For example, by making all the red cells large, and all the others small, the animals can produce a red colour over its body, to signify that it is angry.
Old Mirrors
The mirrors used by the ancient Greeks and Romans, were simply slightly convex discs of metal, bronze, tin, or silver, that reflected light off their highly polished surfaces. Mirrors of clear glass first appeared around 1300 AD in Venice. They were backed by a thin layer of shiny metal that reflected light.
Inside View
Doctors can now look inside our bodies by using an instrument called the endoscope. An endoscope typically employs two types of optical fibres. A central bundle of complex fibres transmits the image from inside the body, while an outer circle of simple fibres projects enough light inside the body cavity to make the image visible. Sometimes, a third set of fibres transmits a laser beam, which can be used to perform small-scale opera-tions within organs or tissue
Fire Box
When you strike a match against the matchbox, a chemical reaction produces a flame. Most matches and match-boxes have compounds of phosphorous that catch fire when being exposed to air. In fact, early matches used to catch fire without being struck, but this was dangerous. So, modern matchboxes use' safety' matches that light only on being struck.
Inside a Bulb
An ordinary bulb has a coiled filament made of a material known as tungsten. The filament is surrounded by gases like argon at low pressure. When electricity is applied to the bulb, it passes through the contacts, rods, and filament, and electrical energy is converted into light.
Swan's Lamp
Swan's Lamp
Swan's lamp had a carbon filament inside a glass bulb. When a current was passed through the bulb, the filament glowed. Swan's house in England was the first in Ithe world to be lit by a light bulb, and the world's first electric light illumination in a public building was for a lecture Swan gave in 1880.
The First Laser
The first working laser was built in 1960 by Theodore Maiman. Did you know that the woi LASER stands for 'Light Amplificati by Stimulated Emission of Radiation'?
Celluloid Film
In 1884, George Eastman of the United States invented a photographic film made of celluloid. It was strong but flexible enough to be wound into a roll. Within a decade, celluloid film was used not just for still photography, but to make movies as well.
Cutting Lights
Long wave laser light is a very effective cutting tool. The beam can be directed to a surface so as to produce intense heat in a small area. This heat can cut through even steel. Laser light never becomes blunt like ordinary metal cutting tools, which is a very great advantage indeed.
Light Pressure
Light is made up of particles that exert pressure which is so little as to be insignificant. Sir William Crookes, a scientist proved this with a device known as a radiometer. In this device, light was used to turn a set of finely balanced vanes, but when all the air was removed from the device, the vanes stopped moving. This showed that the pressure of light alone could not move the vanes.
Electrochromic Glasses
A new type of glass, called electrochromic glass, is covered by a thin coating of a special material which can be turned blue by passing electricity through it. It is used in car rearview mirrors to reduce headlight glare at night. It can also used in windows to control the amount of light let into a room.-Dev Nath
Natural Clocks
Some flowers will open and close their petals at a particular time everyday- almost though they have built- in clocks! Bats and insects have realized this and will come to suck honey from the flowers at that time.
X-Rays
X-Rays are waves of light we cannot see, but which carry more energy than visible light. They can pass through the soft parts of our body, but not through bone. X-Rays are used to show doctors what is going on inside your body, like whether you have fractured a bone or not. - Sneha Rao
Cosmic Rays
Cosmic rays are highly energetic particles that originate in outer space. They are born from clouds of gas surrounding the ancient and massive explosions of distant stars, and they slam the Earth's upper atmosphere at very high speeds.
Gamma Rays
Gamma rays have very short wavelengths. They carry very large amounts of energy, and can penetrate even metal and concrete. High levels of these rays are very dangerous, and can kill living cells. Because gamma rays can kill living cells, they are used to kill cancer cells without having to resort to difficult surgery. Gamma waves are generated by radioactive atoms and in nuclear explosions.
Light to Lead
In ancient times, people made fires at the edge of the water to warn boats of dangerous rocks and shores. Later, light-houses were built to serve this purpose. The first proper lighthouses were built by the pharaohs of Alexandria.
Auroras
The word 'aurora' means 'dawn' in Latin. Auroras are spectacular displays of light seen in the sky over the Polar Regions. They are caused when tiny electrically charged particles from the Sun collide with the atoms in the Earth's atmosphere.
Protection for the Retina
The pupil is a tiny hole in front of the iris that controls the amount of light entering the eye. This is important, because too much light can cause damage to the retina.
Night Vision
People who have to work in the dark often wear night vision goggles. These goggles are designed on the principle that even in pitch darkness, there is some reflected light, which we cannot normally see. Moreover, all objects give off 'heat' energy, which is not visible to the human eye. Night vision goggles are designed to collect and amplify all those tiny bits of available light so that our eyes have enough light to see in the dark. This is called image enhancement technology. The other technology used in night vision equipment is called thermal imaging. It takes advantage of the infrared light given off by objects, which is not visible to human eyes.
Tricky Sunlight
During the day, sunlight looks golden. However, as sunset approaches, the light takes on orange and red hues. This is because the rays become more slanting and have to travel sideways through more layers of air. As this happens, more and more of blue light, which has a shorter wavelength is absorbed and only the colours with longer wavelengths like orange and red are seen.
Improving Vision
For almost 700 years, spectacles have helped people with poor eyesight to see better. Spectacles with convex lenses help people with long sight, to see nearby objects more clearly. concave lenses are used by people with short sight, so that they can see far off objects more clearly.
Contact Lenses
A contact lens is a thin lens that is placed directly on the eye to improve vision. These lenses float on a film of tears in front of the cornea and are today made of plastic or silicon. Like spectacles, they are used to correct a variety of vision problems including myopia and astigmatism.
Why Diamonds Glitter
Diamonds behave like prisms. When light passes through a cut diamond, it is bent into different wavelengths, and the colours separate, and then are reflected back out. Since a diamond's shape is different from a prism's, the colours don't appear in Straight rows, but more like shards of colour as in a kaleidoscope. As a diamond moves, the shards of colours change like in a kaleidoscope, making the diamond glitter.
Galileo's Telescope
Galileo's earliest telescope contained two lenses-a convex lens, and a smaller concave eyepiece lens. Galileo used his telescopes to look at the Moon, the planets, and the stars.
Colourful Communcation
The octopus, cuttlefish, and squid have special cells that are filled with different coloured pigments. The size of these cells can be controlled by the brain. For example, by making all the red cells large, and all the others small, the animals can produce a red colour over its body, to signify that it is angry.
Old Mirrors
The mirrors used by the ancient Greeks and Romans, were simply slightly convex discs of metal, bronze, tin, or silver, that reflected light off their highly polished surfaces. Mirrors of clear glass first appeared around 1300 AD in Venice. They were backed by a thin layer of shiny metal that reflected light.
Inside View
Doctors can now look inside our bodies by using an instrument called the endoscope. An endoscope typically employs two types of optical fibres. A central bundle of complex fibres transmits the image from inside the body, while an outer circle of simple fibres projects enough light inside the body cavity to make the image visible. Sometimes, a third set of fibres transmits a laser beam, which can be used to perform small-scale opera-tions within organs or tissue
Fire Box
When you strike a match against the matchbox, a chemical reaction produces a flame. Most matches and match-boxes have compounds of phosphorous that catch fire when being exposed to air. In fact, early matches used to catch fire without being struck, but this was dangerous. So, modern matchboxes use' safety' matches that light only on being struck.
Inside a Bulb
An ordinary bulb has a coiled filament made of a material known as tungsten. The filament is surrounded by gases like argon at low pressure. When electricity is applied to the bulb, it passes through the contacts, rods, and filament, and electrical energy is converted into light.
Swan's Lamp
Swan's Lamp
Swan's lamp had a carbon filament inside a glass bulb. When a current was passed through the bulb, the filament glowed. Swan's house in England was the first in Ithe world to be lit by a light bulb, and the world's first electric light illumination in a public building was for a lecture Swan gave in 1880.
The First Laser
The first working laser was built in 1960 by Theodore Maiman. Did you know that the woi LASER stands for 'Light Amplificati by Stimulated Emission of Radiation'?
Celluloid Film
In 1884, George Eastman of the United States invented a photographic film made of celluloid. It was strong but flexible enough to be wound into a roll. Within a decade, celluloid film was used not just for still photography, but to make movies as well.
Cutting Lights
Long wave laser light is a very effective cutting tool. The beam can be directed to a surface so as to produce intense heat in a small area. This heat can cut through even steel. Laser light never becomes blunt like ordinary metal cutting tools, which is a very great advantage indeed.
Light Pressure
Light is made up of particles that exert pressure which is so little as to be insignificant. Sir William Crookes, a scientist proved this with a device known as a radiometer. In this device, light was used to turn a set of finely balanced vanes, but when all the air was removed from the device, the vanes stopped moving. This showed that the pressure of light alone could not move the vanes.
Electrochromic Glasses
A new type of glass, called electrochromic glass, is covered by a thin coating of a special material which can be turned blue by passing electricity through it. It is used in car rearview mirrors to reduce headlight glare at night. It can also used in windows to control the amount of light let into a room.-Dev Nath
Natural Clocks
Some flowers will open and close their petals at a particular time everyday- almost though they have built- in clocks! Bats and insects have realized this and will come to suck honey from the flowers at that time.
X-Rays
X-Rays are waves of light we cannot see, but which carry more energy than visible light. They can pass through the soft parts of our body, but not through bone. X-Rays are used to show doctors what is going on inside your body, like whether you have fractured a bone or not. - Sneha Rao
Cosmic Rays
Cosmic rays are highly energetic particles that originate in outer space. They are born from clouds of gas surrounding the ancient and massive explosions of distant stars, and they slam the Earth's upper atmosphere at very high speeds.
Gamma Rays
Gamma rays have very short wavelengths. They carry very large amounts of energy, and can penetrate even metal and concrete. High levels of these rays are very dangerous, and can kill living cells. Because gamma rays can kill living cells, they are used to kill cancer cells without having to resort to difficult surgery. Gamma waves are generated by radioactive atoms and in nuclear explosions.
Friday, December 13, 2013
light:Why is laser light special?
Why is laser light special?
Lasers are a special form of light. Laser light does not exist in nature.
Ordinary light, like sunlight, is made up of many different wavelengths, or colours, of light. If you put all the different colours together, you get white light.
On the other hand, the light from a laser contains exactly one colour or wavelength rather than a lot of different wavelengths. So, laser light is said to be `monochro matic,' meaning of one colour.
In laser light, all the high points or crests of the waves, and the low points or troughs are lined up, so that the waves move together, or are said to be 'coherent.'
Moreover, while light waves from ordinary sources such a,. light bulbs, or the Sun spread out in all directions, laser light waves all travel in the same direction, exactly parallel to one another. This means that laser light beams are very narrow, and can be concentrated on one tiny spot. This property makes the laser light 'collimated.'
The focused power makes laser light useful for cutting and welding. It also makes it possible to control laser light very precisely, and make it do all kinds of useful things. Laser light is truly a wonderful thing- and only human technology can create it!
Lasers are a special form of light. Laser light does not exist in nature.
Ordinary light, like sunlight, is made up of many different wavelengths, or colours, of light. If you put all the different colours together, you get white light.
On the other hand, the light from a laser contains exactly one colour or wavelength rather than a lot of different wavelengths. So, laser light is said to be `monochro matic,' meaning of one colour.
In laser light, all the high points or crests of the waves, and the low points or troughs are lined up, so that the waves move together, or are said to be 'coherent.'
Moreover, while light waves from ordinary sources such a,. light bulbs, or the Sun spread out in all directions, laser light waves all travel in the same direction, exactly parallel to one another. This means that laser light beams are very narrow, and can be concentrated on one tiny spot. This property makes the laser light 'collimated.'
The focused power makes laser light useful for cutting and welding. It also makes it possible to control laser light very precisely, and make it do all kinds of useful things. Laser light is truly a wonderful thing- and only human technology can create it!
light:curious fact
curious fact
Magic Flames
Have you heard of the term 'will o'the wisp'? It refers to a flame that is often seeing moving by itself over marshy areas - quite an eerie phenomenon. There is a simple explanation for this however. The rotting plants in a marsh or swamp produce a gas called methane, while the remains of rotting animals produce a gas called phosphine. When phosphine meets the air, it causes a spark, and this spark ignites the methane that is present, creating a naturally occurring flame. The flame moves quickly over the marsh as the methane catches fire in different places.
Moonlight
The biggest object that bounces sunlight is the Moon. Though we talk of moonlight, the Moon has no light of its own. It merely reflects light from the Sun.
Sun Time
Sundials were used by many ancient cultures to help the people know what time it was. A stick was pushed vertically into the ground, and the time of the day could be calculated by seeing where its shadow fell.
Eyes over Water
The mudskipper, a small fish that spends much of its time on land hunting for food, has eyes that pop up like twin periscopes when it goes into the water. These eyes sit on stalks, and periscope above the surface, while the rest of the mudskipper remains safely underwater.
Dog's Vision
Until recently, it was thought that dogs didn't see any colour at all. Recent studies now show, however, that dogs can differ-entiate between red and blue and can even pick out subtle differences in shades of blue, and violet.
Origin of 'Lens'
A convex lens is flat and round, with sides that bulge outwards. It resembles a lentil seed from which the word 'lens' originates.
Achromatic Lenses
An achromatic lens has two lenses made of different types of glass. One splits the colours, and the other brings them together again. The purpose of this lens, invented in1733 by Chester Moor Hall, was to prevent colour separation.
Hooke's Microscope
Robert Hooke made compound micro-scopes containing two, or sometimes three lenses. In 1665, he looked at a sliver of cork through his microscope and noticed some 'pores' or 'cells' in it. He was the first person to use the word 'cell' to describe the basic unit of life.
Upside down Rainbows
Very rarely, we can see an upside down rainbow. This is an unusual phenomenon caused by sunlight shining through a thin, visible screen of tiny ice crystals high in the sky.
Objects in Water
An object that is seen in water is actually a virtual image of the object. Though the rays of light are bent as they travel from water to air, our eyes continue to follow the rays as though they have travelled in a straight line. So what we see is not the Actual object, but its image.
Soap Bubbles
A soap bubble reflects a spectrum of beautiful colours when illuminated by natural or artificial light sources. This is because the light is reflected from two surfaces- the inner and the outer-of the bubble
Coloured Shells
The inside of some shells have thin layers of hard mineral called nacre. Each layer reflects light, and the reflected rays interfere with each other to create silvery colours.
Binoculars
Binoculars have two pairs of prisms so that light is sent back and forth as it is reflected four times. The prisms turn the image so that it is the right way round, and also the right way up. This makes it possible for binoculars to be shorter than telescopes.
Camera Eye
The Copila is a marine animal that has eyes which work like television cameras do. It has two lenses and a retina that scans each image 10 times for better picture quality.
Solar Cells
Solar or photo-voltaic cells convert solar energy into electricity. Solar cells are used for different purposes.
RADAR
The word RADAR is the short form of the term Radio Detection and Ranging. A radar scanner emits very short radio waves .Objects in the path of these waves send back echoes that are picked up by the scanner.
Peacock's Feathers
The many colours of the peacock's feather, which usually include shimmering greens and blues, are the result of a phenomenon called interference. Interference is the reflection of light on each feather's tiny, bowl-shaped indentation, which reflects the light and causes the colour to shimmer.
Nagative to Positive
William Fox Talbot was one of those who pioneered the technique of making photographs in the 1830s. He soaked paper in a chemical called silver chloride that darkens when exposed to light. When light fell on the paper, it produced a nagative image of the object before it. By using the same process to copy the nagative, a positive print was obtained.
.
Magic Flames
Have you heard of the term 'will o'the wisp'? It refers to a flame that is often seeing moving by itself over marshy areas - quite an eerie phenomenon. There is a simple explanation for this however. The rotting plants in a marsh or swamp produce a gas called methane, while the remains of rotting animals produce a gas called phosphine. When phosphine meets the air, it causes a spark, and this spark ignites the methane that is present, creating a naturally occurring flame. The flame moves quickly over the marsh as the methane catches fire in different places.
Moonlight
The biggest object that bounces sunlight is the Moon. Though we talk of moonlight, the Moon has no light of its own. It merely reflects light from the Sun.
Sun Time
Sundials were used by many ancient cultures to help the people know what time it was. A stick was pushed vertically into the ground, and the time of the day could be calculated by seeing where its shadow fell.
Eyes over Water
The mudskipper, a small fish that spends much of its time on land hunting for food, has eyes that pop up like twin periscopes when it goes into the water. These eyes sit on stalks, and periscope above the surface, while the rest of the mudskipper remains safely underwater.
Dog's Vision
Until recently, it was thought that dogs didn't see any colour at all. Recent studies now show, however, that dogs can differ-entiate between red and blue and can even pick out subtle differences in shades of blue, and violet.
Origin of 'Lens'
A convex lens is flat and round, with sides that bulge outwards. It resembles a lentil seed from which the word 'lens' originates.
Achromatic Lenses
An achromatic lens has two lenses made of different types of glass. One splits the colours, and the other brings them together again. The purpose of this lens, invented in1733 by Chester Moor Hall, was to prevent colour separation.
Hooke's Microscope
Robert Hooke made compound micro-scopes containing two, or sometimes three lenses. In 1665, he looked at a sliver of cork through his microscope and noticed some 'pores' or 'cells' in it. He was the first person to use the word 'cell' to describe the basic unit of life.
Upside down Rainbows
Very rarely, we can see an upside down rainbow. This is an unusual phenomenon caused by sunlight shining through a thin, visible screen of tiny ice crystals high in the sky.
Objects in Water
An object that is seen in water is actually a virtual image of the object. Though the rays of light are bent as they travel from water to air, our eyes continue to follow the rays as though they have travelled in a straight line. So what we see is not the Actual object, but its image.
Soap Bubbles
A soap bubble reflects a spectrum of beautiful colours when illuminated by natural or artificial light sources. This is because the light is reflected from two surfaces- the inner and the outer-of the bubble
Coloured Shells
The inside of some shells have thin layers of hard mineral called nacre. Each layer reflects light, and the reflected rays interfere with each other to create silvery colours.
Binoculars
Binoculars have two pairs of prisms so that light is sent back and forth as it is reflected four times. The prisms turn the image so that it is the right way round, and also the right way up. This makes it possible for binoculars to be shorter than telescopes.
Camera Eye
The Copila is a marine animal that has eyes which work like television cameras do. It has two lenses and a retina that scans each image 10 times for better picture quality.
Solar Cells
Solar or photo-voltaic cells convert solar energy into electricity. Solar cells are used for different purposes.
RADAR
The word RADAR is the short form of the term Radio Detection and Ranging. A radar scanner emits very short radio waves .Objects in the path of these waves send back echoes that are picked up by the scanner.
Peacock's Feathers
The many colours of the peacock's feather, which usually include shimmering greens and blues, are the result of a phenomenon called interference. Interference is the reflection of light on each feather's tiny, bowl-shaped indentation, which reflects the light and causes the colour to shimmer.
Nagative to Positive
William Fox Talbot was one of those who pioneered the technique of making photographs in the 1830s. He soaked paper in a chemical called silver chloride that darkens when exposed to light. When light fell on the paper, it produced a nagative image of the object before it. By using the same process to copy the nagative, a positive print was obtained.
.
light:Why does an electric bulb make a bang when it is broken?
Why does an electric bulb make a bang when it is broken?
Have you ever noticed the breaking of an electric bulb and the consequent bang? This sound is produced by the air surrounding the bulb.
The inside of an electric bulb is vacuum. So, the pressure inside is lower than that of the outer atmosphere. When the bulb is broken, air rushes in at high speed from all sides to fill up the vacuum. The sudden surge of air produces a bang.
An electric bulb produces light when its filament is heated at a high temper-ature. The vacuum inside the bulb prevents the filament from oxidizing with air.
Have you ever noticed the breaking of an electric bulb and the consequent bang? This sound is produced by the air surrounding the bulb.
The inside of an electric bulb is vacuum. So, the pressure inside is lower than that of the outer atmosphere. When the bulb is broken, air rushes in at high speed from all sides to fill up the vacuum. The sudden surge of air produces a bang.
An electric bulb produces light when its filament is heated at a high temper-ature. The vacuum inside the bulb prevents the filament from oxidizing with air.
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