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.