Wednesday, July 21, 2010

The Mystery of Force Fields!

The day was little breezy. Professor Govind was busy soldering the transistors on his new invention. The television was switched on and Sheela was there easing on the sofa, watching an episode of "Star Trek". It was indeed a nice episode. An asteroid was heading towards the small space ship in terribly high speed. The crew felt the danger of the asteroid hitting the space ship. Everyone was puzzled.

The captain shouted "Shields up!"

No sooner he shouted, than a thin bluish layer enclosed the space ship. It shattered up the asteroid into pieces then.
"Phew!, that's the end", exclaimed Sheela in amazement. "Professor, what actually is a force field?"Sheela's question attracted his attention. He started then, 
" Force fields are thin impenetrable barriers which could destroy or reflect everything that fell on them. Be it a stone, metal piece, water or even laser."
"Just have a look at this photograph. It looks like this", he showed her.

"The principle behind this force field is a simple theory. You might have seen your Plasma television screen. The same goes here- the principle of isolating air from vacuum", he paused to take out something from his junk box.
"Oh!, But Professor,what is that we call "plasma"? interrogated Sheela.

"I'll rather show you off", said Prof.Govind and took a hollow glass sphere, in which a metal electrode is inserted. He said, "Sheela, this glass bulb contains a mixture of Helium and Neon gases at very low pressure," while connecting its terminals to 5000V a.c. supply of high frequency(about 35 kHz). The bulb started glowing and violet streaks started appearing in it.
"Wow!" wondered Sheela.
He said, "Before the matter inside the bulb were in gaseous state. But, as soon as we started applying electric potential, the gases will be ionized completely. And this state in which gases are completely ionized is called "Plasma state" the forth state of matter" and touched the glass bulb. White streaks appeared from the filament to the point where he touched the bulb.
"Is there any chance that I get shock while touching this bulb, professor?" asked Sheela."Actually the glass here behaves are dielectric between the ionized air inside and my hand(both being a conductor, this setup behaves like a capacitor). 
Leaving this setup intact, he took a strong horseshoe magnet and placed it near iron filings. Sheela smiled and said, "I knew that magnets attract charged bodies already in my grade-5". 
"That's the matter. So we have ions that are charged, haven't we? Just imagine that this magnet attracts these ions completely to one side thereby creating vacuum at the center.We get a plane of ionized gases on the corner." 
The same principle is used in plasma windows.

"This plasma window can be used in combination with a series of laser curtains and carbon-nanotubes to generate a powerful force field around us. But to stop laser, one must deal with photochromatics", said Prof.Govind.
"Photochromatics?" interrogated Sheela.
"Yeah. It is the science based on the fact that certain materials can exist in two different forms. Say your sunglasses. How does it become black on exposure to the sun?" puzzled professor Govind.
"How?" asked Sheela. 
The glass is coated with a thin film of photochromatic materials which when exposed to radiations like UV rays becomes dark(colored) due to a change of state. Similarly, specially designed material has to be used to selectively stop lasers or else, you'll go blind on dark while you're in force fields."

"Hmm. That was interesting!" exclaimed Sheela. "Anyway, it's time for the dinner. Thank you professor. I must go now." 
"It's been a great time explaining you about this. Pleasure!" said the professor and got back to his workshop.

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