Archive for October, 2007

Double slit experiment

Saturday, October 13th, 2007
Double slit experiment by Tonomura
Double slit experiment by Tonomura, 1989.
Fig. from Wikimedia Commons

Double slit experiment of electron showed an interesting behavior of electron. The setting of this experiment is simple : Electron gun, double slit, and screen. An electron that is shoot from electron gun pass through one of the slit, hit a screen, and remain as a dot. What happen?

In a real world, if one shoot a gun to a double slit, then bullet marks on a screen are made where visible between the slit, that is, intersection of a gun-slit-screen line-of-sight and the screen. What one see is only two lines associated with the double slit.

The figure in right is a result of double slit experiment of electron by Tonomura in 1989. Number of electron is (a) 10, (b) 200, (c) 3,000, and (d) 70,000, respectively. The results are beyond imagination. In the beginning, the bullet mark appears not like gun shoot in real world, but at random. Interestingly, after enough number of shot, it shows interference pattern as seen in figure (d). Such interference pattern is characteristic of a “wave”, and not “particle”. This is a proof of the electron posses behavior of both “particle” and “wave”, simultaneously. Such particles (?) are called as “quantum”.

What I can learn from this experiment? I write many index cards along PoIC. For me, the dots correspond to the individual index cards.

At the very beginning of using PoIC, index cards are like totally random shot (a). After a month, number of index cards increase 100 - 300, still random (b). By keep writing, I see a blur pattern after 6 months (c). The blur pattern become clear and clear after a year (d). I don’t say we need 70,000 index cards to see pattern, but lager number is better anyway.

I said “do not classify, do not search, do not revise chronological order” in the manual. Because it is hard to find a pattern at the beginning stage for anyone, as finding pattern in figure (a), (b), and even (c). After enough number of dots accumulates as shown in figure (d), it is much easier to see the pattern. This is time to organize Task Force.

To create something new, what we see at beginning is quite blur. Because we don’t know it exactly. That is something “new” which does not exist yet. It doesn’t have name yet. No way to classify. We cannot predict what idea comes next. It is “apparently” random, but not random in fact. All we can do is just write index cards one by one, like shooting electron.

Unfortunately, some people stop using PoIC before seeing pattern. What they saw is only random pattern like (a), (b), and they return to nothing. Find a pattern or not is just owe to ourselves.

What nature tell is that we needs enough number of dots (index cards) and enough time to see pattern.

Ref. : @wikipedia, Double slit experiment,
Ref. : @web, Tonomura’s double slit experiment