The electron really always waves at you

First, a couple of notes, touching on the topic I discussed the last time.

1. Yesterday, I did unpack one of the cartons in which I had packed some of the books while making the move from Mumbai to Pune (after my job less in January this year). Turns out that Feynman’s QED book was right in this first carton that I opened!

So, I immediately consulted the index at the end of the book, and then went over the pages related to “diffraction.” The diffraction-related footnote is on p. 59, though Feynman begins the discussion of diffraction mainly from p. 53. (The index mentions p. 46–49, but that passage is mostly about diffraction grating, not about electrons or photons going through a single slit.)

However, even in this footnote, Feynman does not directly state that those outer fringes do make an appearance in the single-slit diffraction. The last time, I thought he does clarify the matter. So, there must have been a confusion in my recall.

The uncertainty principle is dealt with in the footnote beginning on p. 55. Chances are, I confused between his indirect denial of the uncertainty principle (which is present), and a noting about the outer fringes (which is not). Possible. My memory, I keep telling you, is not much reliable.

2. I then tried to recall where I had read the analogy between (i) the classical particles with the example of bullets and (ii) the quantum mechanical electron.

I now realize that, in an at least indirect way, it is none other than Feynman himself!

In his Lectures book, III volume, first chapter (the same one I referred to the last time!), Feynman first takes the example of bullets and draws a probability curve; see figure 1 (b) here [^]. He then draws an exactly analogous (i.e. misleading) probability curve—the one just one central band—for water waves, in figure 2(b), and then, also for the electrons, figure 3 (b).

Though Feynman does not directly make any statement to the effect that the single-slit diffraction has only a single band, it is obvious from the flow of the contents of his lecture—in particular, the more or less direct analogy to the bullets—that he makes it far too easier for people to draw the sort of wrong conclusions which we discussed the last time.

Feynman, thus, makes QM sound more mysterious than it actually is.

[And, of course, since it’s Fyenman, Americans, esp. Californians, will never agree with me on the last statement.]

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On another note, in the course of attempting to build a computer simulation, I have now come to notice a certain set of factors which indicate that there is a scope to formulate a rigorous theorem to the effect that it will always be logically impossible to remove all the mysteries of quantum mechanics.

… Yes, you read it right. … More on it, later!

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A Song I Like:
(Hindi) “uljhan sulajhe naa…”
Singer: Asha Bhosale
Music: Ravi
Lyrics: Sahir Ludhiyanvi

 

[E&OE]

 

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