# Double Slit Experiment

1. Apr 20, 2015

### PZIG98

A few question about the double slit experiment... I have watched many videos and discussions about this experiment and am curious if anyone has ever varied the slits... What happens if one slit is vertical and one horizontal? If they are closer together or further apart? One fat and one skinny? One tall, one short? etc etc... How about three slits? or maybe concentric circular slits? I would imagine that this has been done and the results unremarkable but I have not heard or read anything other that one or two slits... How about two emitters side by side with zero slits? Would an interference pattern result?

2. Apr 20, 2015

### DrChinese

I can't find the relevant reference at this moment, but the physical shape of the slits affects the shape of the resultant image. if you used a diamond shape instead of vertical bars, it would change the pattern to resemble diamonds. A horizontal bar results in overlaps.

3. Apr 20, 2015

### PZIG98

Do the slits determine the period of the interference pattern?

If two photons where fired from two separate emitters, at the same time with no slits, would an interference pattern result?

4. Apr 20, 2015

### DennisN

Hi PZIG98,
Yes, it has been done. Here is also a thread with a document and some pictures:

And here is a clip from MIT - an introduction to the experiment, including some variations:
http://video.mit.edu/watch/thomas-youngs-double-slit-experiment-8432/

EDIT:
See the clip I posted above .

Last edited: Apr 20, 2015
5. Apr 20, 2015

### Ponderer

In order to see an interference pattern the frequencies of both lasers must be nearly the same. If for example the frequency difference between the lasers is 1Hz, then you'll see the interference pattern cycling every second. To give you an idea how stable such a laser would have be, a 650nm red laser is 4.6E+14 Hz. A difference of 1Hz is unheard of. The temperature drift alone is far greater.

Last edited: Apr 20, 2015
6. Apr 21, 2015

### zonde

7. Apr 21, 2015

### PZIG98

Makes sense to me about the frequencies... How are experimenters certain that they are firing 1 photon at a time when doing the double split? Seems the me that the "Uncertain" nature of these particles would make that impossible... Would seem more likely that what is happening is really a, "small number" are fired at each time...

8. Apr 21, 2015

### DrChinese

It depends on what effect you are looking for. There are ways to be certain that only one photon is present within a specified time window; an example would be to use heralded photons. Other times you simply want the average to be "close enough" to one. That can be accomplished with a suitably low intensity.

You can be sure that the experimenter is aware of this point, as it can make a difference to the outcome.

9. Apr 21, 2015

### PZIG98

I appreciate you and others taking the time to entertain my curiosity...
If both slits are observed, measured... the wave/waves/pattern remains collapsed I assume?

How is the emitter focused/aimed. Trying to understand why they sometimes go through this side and sometimes the other. I assume most times they go through neither? Or, are they focused on a particular point on the partition?