It seems this topic is a bit 'heavy' for discussion

But let me just add two interesting bits of information:
1) Scientists have succeeded in slowing down a ray of light
2) They have also succeeded in speeding up a light ray by 300 times by passing it through a chamber containing Cesium vapours.

Umm.. My physics is as rustic as can be... btu then what has ever stopped me from pondering and talking about things I have absolutely no idea about..
Light as I remember is another form of energy, and can be transformed easily. When an object obstructs the path of light the light particles would collide with it and would result in trnasformation of a differnt form. Keep your hand for long time in a strong beam, and you would feel the transformation to heat energy, due to those constant collisions. So figuraively those packets fall at your hands rahter than feet .
Same is exhibited but fading clothes.

though I would have to read more about the experiments mentioned. Do you have the link??

Also, about "vanishing" an object by throwing a beam of light on it... isnt it that whether an object is transparent or opaque is quality of the object rather than the light.
Are you suggesting that same light or different light can change the physical properties of an object?
umm..

Stop light

18:49 18 January 2001
From New Scientist Print Edition.
Eugenie Samuel, Boston
Scientists have stopped light in its tracks in two landmark experiments. In doing so they have overcome a fundamental obstacle to the development of quantum computers.

Light normally travels at 300,000 km per second but both groups of researchers slowed a laser beam to a complete standstill by passing it through a specially prepared cell of gas atoms. Later the researchers restarted the light beam and sent it speeding off again.

Ron Walsworth from the Harvard Smithsonian Centre for Astrophysics led one of the groups and says the demonstration shows how information could be transported in a quantum computer. "The light could take information from node to node as required," he told New Scientist.

"Everybody thought it was pretty wild," says Seth Lloyd, a quantum computing engineer from MIT who attended the Physics Optics and Electronics conference in Utah where the Smithsonian group presented their idea. "We thought it would be what's needed in quantum computing."

Steady state
In conventional quantum computing, researchers aim to store quantum states in individual atoms. However the states are very delicate and liable to be destroyed by background noise.

In contrast, in the light stopping experiment, the information is contained in the electromagnetic fields of the light beam and is transferred to the state of the gas atoms. "We have over 1012 atoms which makes the state very robust," says David Phillips, who worked on the experimental set-up at Harvard-Smithsonian.

Both Phillip's group and Lene Hau's at Harvard University and the Rowland Institute in Cambridge, Massachusetts, prepared their gas atoms in the same way. They used a control laser beam tuned at just the right frequency to put the atoms into a so-called dark state. In this state the atoms cannot absorb light as usual.

When a second pulse beam is passed into the cell, rather than being absorbed it interacts with the atoms by flipping their spins. Doing this slows the beam by an amount that depends on the intensity of the control beam.

So to slow the beam to a standstill, the researchers fade out the control beam completely. But they have to do it smoothly or the dark state is destroyed. "Showing that could be done was the clever theory," says Phillips.

This theoretical breakthrough was achieved in 2000 by Misha Lukin and Suzanne Yellin at Harvard-Smithsonian and Michael Fleischhauer at the University of Kaiserslautern, Germany.

The Walsworth-Lukin work will be published in Physical Review Letters and Lene Hau's experiment will be reported in Nature.



Shivani you can find this article at www.newscientist.com

I guess it is simpler to give you a link to the article, as the article is rather big, and not so interest-evoking

You can read about the speeding up of light here:
http://partners.nytimes.com/library/nation...sics-light.html

If a beam of white light from a torch can light up an object on the table in a dark room, is it possible to 'vanish' an object on the table in a brightly lit room by using a torch that emits 'black light' so to say? (Here I am not referring to the 'black light' that is used commonly)


.... madrake bandhu ... I need a detailed explanation on these... plz forward me some material or direct link :-)

Thanks in advance

SAchin

Sorry Sachin, I did not understand your request. My point was simple. If we are in a dark room, and switch on a pencil torch. The beam falls on a vase on the table. Now we can see only the vase. Since the light is not very powerful, the remaining room is still dark. So effectively we are only seeing the vase.
The beam of light showed us only the vase and nothing else.

I reverse the scenario. The entire room is brightly lit. Now if I know something which can change the properties of light (just some words to explain), can I use a pencil torch that emits a beam of 'black light' or 'anti-light' or whatever, which if directed at that vase, will render it invisible?