# B A double slit question or two

1. Feb 4, 2017

### hsdrop

Does it matter what the slits are made of? Do different kinds of matter make difference interference patterns on the wall? Also I know, part of that cause waves in the water is the surface tension. Does some kind of surface tension come into play with the double slit experiment waves of interference patterns?

2. Feb 4, 2017

### Roger Dodger

The interference is caused by the restrictions on the possible paths that light can take when going from the source to the screen. Essentially, the light "samples" all possible paths it can take to reach a certain point on the screen. How these paths interfere with each other determines the chance the light will reach that point. So the choice of material doesn't matter and surface tension isn't an issue. I would highly recommend Richard Feynman's book QED to understand what is taking place. It's relatively cheap and easy to understand. It also has almost no math.

3. Feb 4, 2017

### hsdrop

Ok I get that is what's going on with the light waves or what ever els one would be shooting through the slits. I'm just questing if anyone had tried different materials to see if there was a difference. I also was wondering what kind of an emitter and how strite does the emitter shoot at the slits?

4. Feb 4, 2017

### DrChinese

There's no theoretical reason it would make a contribution worth studying. And if anyone had studied that, it would not be worth much to report as a null result.

Things like the shape and incident angle would alter the shape/positioning of the resulting pattern.

5. Feb 5, 2017

### hsdrop

hmmmm ok I'm just trying to figure out the similarities between partial waves and liquid waves if there is any beside the general shape. I'm still left wondering if there is any kind of surface tension like action in the partial waves that can be noticed?

I just wanted to say thank you again for taking the time to answer my questions, for me without asking thing like this I could not learn about the world around us.

6. Feb 5, 2017

### Thejas15101998

what are "partial waves" ?

7. Feb 6, 2017

### hsdrop

If you're wondering what in refering to look up wave-particle duality.

As for my other questions, I really would appreciate so kind of answers. If I'm asking questions that have not been asked before (which I'm almost sure that I am not the first) where can I find the answers then?

8. Feb 6, 2017

9. Feb 6, 2017

### DrChinese

Problem is, there are *some* similarities between light quanta (photons) and liquid waves. However, there are *critical* differences that ultimately render your line of reasoning incorrect. What happens to water waves has no actual bearing on photons, which are covered by completely different theory. There is no such observable thing as "half a photon", for example.

If you are not getting answers, part of the reason is that common language - words such as "waves" - are inadequate to fully explain the situation. It is very common to confuse the common meaning of words describing quantum phenomena with the underlying theory. They are often intended as "shorthand" more than anything. I can describe wave particle duality in terms of the Heisenberg uncertainty principle, but that probably wouldn't help much. That is partially why wave particle duality is outmoded as a term, as has been mentioned.

10. Feb 6, 2017

### hsdrop

I'm sorry for using common words. I have a great difficulty with spelling and grammar when it comes to writing. I tend to shy away from the harder words to spell like "phenomena" so I will try to be more descriptive in my questions.

I know what the Heisenberg uncertainty principle is so you don't have to explain that one. I have bin reading up on the double slit experiment and other experiments that branch off or add to the original double slit experiment. Like the delayed choice quantum eraser experiment. I have noticed that the focus of everyone's attention is eather on the screen or detectors (which I understand why). No one seems to explain what the emitter is or how straight it shoots out particles. I also have some questions about the slit that have been used as well but I'll just ask one question at a time.

11. Feb 7, 2017

### Staff: Mentor

As a small data point, I've done interference and/or diffraction in undergraduate optics labs using slits cut in metal, cardboard, and (I think) plastic, with no unexpected results.

12. Feb 7, 2017

### DrChinese

Most experimental write-ups explain that. Keep in mind that a double slit source must be coherent. You get that with a point-like source or a laser beam. What is it more specifically that you want to know?

13. Feb 7, 2017

It's confusing to read certain things here and contradictory things elsewhere. It's been stated here that the concept of wave particle duality has been outdated for nearly 100 years but a quick search seems to suggest otherwise and that the concept is alive and kicking. In just a few minutes search I found reference to the duality of C60 molecules in a Nature Letter and numerous other references to duality from places which include The American Physical Society, Phys.org, University of Bristol,, Ecole Polytechnique Federale de Lausanne. The list goes on.

14. Feb 7, 2017

### DrChinese

It is still used as shorthand, you are correct. A lot of the folks here have discarded it as unnecessary (which it technically is). It can be useful as an analogy just like many concepts are. However, if you take it too far, the analogy fails. So if it works for you in a particular situation, use it.

The duality is that only one or the other of 2 non-commuting observables can be well-defined. And depending on which, it can exhibit different behavior.

15. Feb 7, 2017

Thank you for your clarification Dr Chinese. That's the way I considered duality to be.

16. Feb 9, 2017

### hsdrop

Thank you for your input and for the info, I'm sure that if anyone was looking to see if there was a difference or not, nothing looked out of place. The reasons I'm asking, I can't find anywhere that anyone has ever compared it or not. I want to get the most accurate image in my head of the experiment, and what happens in it. One last thing about the emitter, just to make sure that I have it right. Parallels of projectiles fired at 2 slits, and the parallel projectiles have to span the length of both out side edges of the slits?

I happy to sketch something up if no one understands what I'm asking