Thursday, 30 April 2009

The Leap to a Quantum State


Hello Reader and welcome to the first segment of 3 all about Quantum Mechanics. Due to the science being so strange, I will cover as much as possible and to make sure you can grasp at least a little of what’s going on.

I will start off with this: We all have heard of Sir Isaac Newton and his Laws of Motion. You may not know the laws but you have heard his name associated with such phrases, I am sure. Newton was the one who came up with the concept of Gravity. And the ever so famous Action, reaction phrase... that was Newton’s Third Law!

Well it turns out; this is fine and dandy for macro scale. Objects that can be seen with the human eye, you, me, space shuttles, cannons, etcetera. But when we get to the micro scale, atoms, this is not right at all. Sub atomic particles move differently. This is where quantum mechanics starts playing a role in science.



In order to understand the next part, you must imagine what a wave looks like. That’s right, go back to High School Trigonometry and try to remember what a sine wave looks like. This is how light travels... in wave form.



Through experiments, it was determined that electrons when separate from the atom, also travelled in a wave. Now isn’t that strange? On a large scale, a bunch of atoms move using Newtonian Mechanics, but if you look at individual particles and sub-atomic particles, they act as waves. They even interfere like waves!


This is known as the particle wave duality. So one question that is out there is can light act like matter? We have not seen light (photon) act like a real particle with mass, but we have seen interactions between sub-atomic particles and a photon. This is what happens when humans perceive light and colour. A certain wavelength of an object is not absorbed and released. This wavelength is what we see. This is due to electrons gaining energy from a photon and then releasing it.

Electrons are weird little buggers. In an atom, the concept taught in High School is that they travel in circles around an atom. This is quite untrue. Instead, their positions are quite unclear. What is known, due to Schrödinger’s wave equations, is that there are probability “clouds” in which an electron could occupy in space and time. They do not stay in one place but “teleport” to another space in the probability cloud. This uncertainty gave rise to Heisenberg’s Principle of Uncertainty. He states that the position multiplied by the momentum of the object has to be larger than a constant. Thus, if one is item is very well know (say the momentum, which is mass x velocity), then the position of the electron cannot be well known.
A reason we cannot detect this is because the sophistication of our technology. A lot of out optical devises uses either photons or electrons to detect object positions. If a photon is what makes an electron excited and do not know the initial characteristics (velocity and position), the conditions cannot be deduced. Hitting an electron with an electron is also quite hard. But doing this does not help, seeming the wave feature of the electron allows it to be random in itself.

That is it for the basics of Quantum Mechanics. As always comments are encouraged.

3 comments:

Adam said...

Best line of the year: "Electrons are weird little buggers." :P
And well said regarding the ridiculous model of individual electron movement that is still taught in lower level chemistry classes...yes, there's beauty in such a simplistic model BUT its unequivocally been shown to be WRONG
so, in closing....nice post :P

Keith said...

Bohr was nice enough to make that model. It was appropriate for the technology available to him. It's just that, as new technology arises so does the outlook on different aspects of the actual atom (eg. Large Hadron Collider and possibly the Higgs Boson). Who know's what new aspect they will find in the next few decades? It'll be fascinating.

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