# How to set up a double slit experiment?

1. Nov 26, 2013

### Fiziqs

I was thinking of finding a new hobby, and thought that playing around with the double slit experiment might be interesting. I was wondering how feasible it would be to set up the double slit experiment, not simply the laser and slit version shown here: https://www.physicsforums.com/blog.php?bt=6320 [Broken], but with all the necessary apparatus to emit particles one at a time, detect them at the slits and then record them on a screen.

(i.e. a TEM costs around $95000) If you have good contacts, you can usually pick up old equipment though. 3. Nov 27, 2013 ### Fiziqs I could see myself investing$100k in a system at some point, but would like to start off more modestly. Would a simple setup of a laser, attenuator, barrier, ccd camera be sufficient to begin with? If so does anyone have any suggestions as to the type of components to use, and any accompanying components that might be necessary. What would be the best type of laser and ccd?

Thanks

4. Nov 27, 2013

### f95toli

The problem is that lasers do not emit single photons: they emit coherent radiation.
Hence, if you want to emit single photons you need to use various tricks, and these generally involve quite a lot of expensive equipment.
And no $100K is still not enough for this;$100K is probably just about enough to buy one of the lasers you would need. Setting up an optical lab from scratch would probably cost clsoer to a $1M (it obviously depends on what you are trying to do, but$1M is probably a good order-of-magnitude estimate).

5. Nov 27, 2013

### Fiziqs

I was thinking that the cost wouldn't be in the laser so much, but rather at the other end in the ccd. I've seen examples of the setup described using a simple 5Mw HeNe laser with maybe a filter, lens, and an attenuator, none of which appear to be all that expensive. As for the ccd, I found this one on ebay: http://www.ebay.com/itm/Photometric...517?pt=LH_DefaultDomain_0&hash=item19e1f362b5, but I'm not sure if this one is what I would need. Or whether this one is insufficient, overkill, or wrong for my application. Which is why I was hoping for some educated input. What is it about the laser that I'm not getting. I don't need a true single photon emitter. I was thinking that a laser with an attenuator should work fine for my purposes.

What type of laser do I need for a hobbyist setup? What type of ccd?

Thanks

6. Nov 27, 2013

### Simon Bridge

The basic bobby setup for diffraction would be a diode laser, a hair, and a wall.
Cost is about \$20 or so.

You have indicated you are interested in low intensity stuff ... do you want to go low enough to have a single photon traverse the apparatus at a time?

So the laser is chosen usually for the frequencies you want.
To get down to one photon at a time - you need a "single photon source"
http://iopscience.iop.org/0034-4885/68/5/R04/

For very low intensity light, you need a photomultiplier.
The lower the intensity of the light, the more expensive the photomultiplier.

You also need a very dark room - if you are wanting to detect single photons you don't want any stray light at all if you can help it. Remember - everything gives off light at some level.

Starting to get the idea why it can get very expensive very fast?

7. Nov 28, 2013

### physics.cie

U need to have a laser light and a card board with two pin holes very close to each other . And screen should be far away from the pin holes. Whole apparatus must be kept in dark..

8. Nov 28, 2013

### Duplex

In that case, I would recommend this setup:
http://video.mit.edu/watch/thomas-youngs-double-slit-experiment-8432/

Apparently OP is an advanced "hobbyist" who want to start at a substantially higher level with one particle at a time and be able to upgrade the equipment from there.

Good luck, Fiziqs.

9. Nov 28, 2013

### DennisN

Thanks for the good clip, Duplex! I will add that link to my blog post about DSE at home (which was mentioned in post #1). I also liked the suggestion on how to make good pin holes (in metal) - I will try that. It's difficult to make good circular pin holes in paper or cardboard - they easily distort the image:

Left: laser through one pinhole in paper, Right: laser through two pinholes in paper.

You may already have experimented with basic optics, I don't know. But if you haven't, I would personally start with buying and experimenting with a relatively cheap basics optics kit for hobbyists to see if I enjoyed it. And with a versatile kit you can do more than just the basic double slit experiment (lenses, mirrors, prisms, polarizers etc). You don't have to start with spending a fortune .

I also want to stress that lasers should be handled with care: Laser safety.

10. Nov 29, 2013

### cryptist

Maybe you can go and ask to use a university's optics lab for one hour or sth. Or you can join to an experimental physics class. It would be much more cheaper and educational I think.