# How to conduct the electron double slit experiment

I am planning to conduct the electron double slit experiment for a project in my school. Even after researching quite a bit online, I wasn't able to find a proper guide that explains the materials and procedure involved in carrying out the experiment. How do I go about conducting it and what do I need for it?

• What resources do you have? A monoenergetic electron beam source would be a good start. – S. McGrew Jul 20 '18 at 4:25
• The electron diffraction in general is done in schools with a purpose built apparatus. It is a CRT with electrostatic deflection that allows the beam to be steered to different slits and grids in a plate between the gun and the screen. I can't recall ever seeing any electron double slit apparatus. – C. Towne Springer Jul 20 '18 at 4:32
• If you're not buying a commercial off the shelf system such as @C.Towne describes, a high quality vacuum system and some practice using it would also be a good start. And some kind of position sensitive electron detector with a suitable resolution (quite a bit higher than typical textbook figures would lead you to believe if you mistake them for being to-scale). – dmckee --- ex-moderator kitten Jul 20 '18 at 4:48

## 1 Answer

I do not think that you have thought through what you are planning to do.

You may have at school an apparatus with which electron diffraction can be demonstrated.
It consists of electron gun probably with a maximum voltage of $\rm 5000\, V$ which fires a stream of electrons at at very thin graphite target.
The electrons then hit a fluorescent screen which emits light when electrons hit it.
The whole apparatus is encased in a glass envelope inside which the is a very low pressure (vacuum).
The vacuum is there so that the electrons can pass between the various parts of the apparatus unhindered by collision with air molecules.
The wavelength of the electrons emitted by such an electron gun is about $1.7 \times 10^{-11}\,\rm m$ and the spacing between the atoms in the very thin graphite sample, which has to be of the same order of magnitude as that of the electrons to get an easily detectable effect, is approximately $1 \times 10^{-10}\,\rm m$.
If the accelerating voltage is decreased then the wavelength of the electrons increases but the brightness of the pattern seen on the fluorescent screen decreases so that below about $1000\,\rm V$ not pattern can be seen on the screen.

So will need an electron gun, a double slit and a means of detection of the electrons with the whole apparatus enclosed in an evacuated chamber.
If you plan to use a fluorescent screen then your slits need to be fairly close together ($\approx 10^{-10}\,\rm m$) and also of small width.

Similar experiments have been done using an apparatus based on an electron microscope and instead of two slits the equivalent of a a Fresnel biprism was used.
Here is one article about such an experiment.

I think that you have chosen an experiment which would be rather hard to do in a school laboratory?