Thread: When You're Dumb, You Just Ask

Maybe these questions are goofy but I feel I need to ask them. Concerns the double slit experiment.

Imagine that the double slit set up, apparatus and all, is duplicated but the size of the Milky Way, proportional in every way to the lab experiment, and instead of electrons we fired tennis balls at it (or something the size of whatever an electron would be if enlarged accordingly) would we get the same results?

In a normal experiment, does it make a difference if the slit’s dimensions are increased (wider)? Are the slits designed to be of a certain size or is there a range of sizes that works? In any case, why?

Originally Posted by zinjanthropos

Maybe these questions are goofy but I feel I need to ask them. Concerns the double slit experiment.

Imagine that the double slit set up, apparatus and all, is duplicated but the size of the Milky Way, proportional in every way to the lab experiment, and instead of electrons we fired tennis balls at it (or something the size of whatever an electron would be if enlarged accordingly) would we get the same results?

In a normal experiment, does it make a difference if the slit’s dimensions are increased (wider)? Are the slits designed to be of a certain size or is there a range of sizes that works? In any case, why?

To answer your first question: No. The simplest way to think of it is that the "wavelength" of an object is inversely proportional to it mass. Macroscopic objects like tennis balls have enough mass to make their " wavelength" magnitudes upon magnitudes smaller than the physical size of the object itself.

Now, as far as the size of the slits are concerned: The slit really needs to be of a width of the same magnitude as the wavelength passing through it. This in of itself shows why the above tennis ball experiment won't work; the width of the slit needed, based on the "wavelength" of the tennis ball, is many, many, many times smaller than the tennis ball that would have to pass through it.

Fundamentally isn't the effect invalidated once you get above the size of sub-atomic particles?

Originally Posted by propoly

Fundamentally isn't the effect invalidated once you get above the size of sub-atomic particles?

No, they have reproduced the effect with C60 buckminsterfullerene: https://physicsworld.com/a/wave-part...-60-molecules/

But indeed that's about the limit, since the wavelength associated with the stream of particles is given by de Broglie's relation λ = h/p , where h is Planck's constant and p is the momentum. So the more mass the entity has, the smaller the wavelength will be for a given velocity. Eventually a point is reached at which the wavelength is too small for measurable effects to be produced.

Chemists are quite used to seeing other effects of wave-particle duality at the scale of whole molecules. The quantisation of molecular rotation, which gives rise to rotational spectra, is another manifestation of it.

Originally Posted by zinjanthropos

Maybe these questions are goofy but I feel I need to ask them. Concerns the double slit experiment.

Imagine that the double slit set up, apparatus and all, is duplicated but the size of the Milky Way, proportional in every way to the lab experiment, and instead of electrons we fired tennis balls at it (or something the size of whatever an electron would be if enlarged accordingly) would we get the same results?

In a normal experiment, does it make a difference if the slit’s dimensions are increased (wider)? Are the slits designed to be of a certain size or is there a range of sizes that works? In any case, why?

Your questions are not goofy at all!

You might enjoy reading an old classic by George Gamow: Mr. Tompkins in Wonderland. The book answers your question and many others by considering how the world would differ if the speed of light and Planck’s constant were different, for example. There are several books in the Mr. Tompkins series, but Wonderland is the one that most directly considers the sorts of things you’re asking about.

Originally Posted by tk421

Your questions are not goofy at all!

Thanks for the encouraging words. Hold that thought but you may change your mind after the next ones:

Back to the double slit. Is it possible to conduct the experiment in such a way using multiple screens so that a wave pattern on one is followed by an impact image on the next and so on. Thinking if I try to measure/observe the particle/electron as it passes through either slit then I would see a double impact image on the back screen. But if you had a slit in each of those impact sites, maybe even a double slit in each, with another screen in behind and you couldn’t or didn’t measure/observe from that point.....would you see a wave pattern on the second screen? Also, do the slits have to be vertical?

New questions: Is super-positioning the unobserved particle/wave state or the particle state when observed? Are the waves slightly different from one another when they go through both slits unobserved?