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.





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