Preamble
Before we start our Journey into the smallest known particles, I want to clarify that all the information in this post is information i collected for my own general knowledge. I´m not a physicist and there will be no bibliography. The reason i´m sharing this post is because i´m fascinated by this topic and i want to share this facsination with you. This here is just a foretaste and i can´t guarantee 100% reliability. If you find it interesting you should inform yourself and i guarantee you´ll find out that this here is just the tip of the iceberg. I´m looking forward to discuss with you about this topic.
Quantum Physics In General
Next to the Theory Of Relativity, Quantum Physics is the second cornerstone of modern physics and deals with the “behavior” of the smallest particles (e.g. photons, electrons etc.).
The Reason why Quantum physics had to be discovered was because conventional physics had reached its limits. Many results out of experiments in the scale of molecular structures and below disagreed with our physical understanding and they still do.
There are a lot of mindblowing and interesting aspects within the Quantum Physics and today we are going to take a closer look at one of them.
But I have to point out that we still aren´t anywhere near of scratching the surface of its whole range. The topic we are going to look at is the Double-Split-Experiment.
Double-Split-Experiment
In this Experiment we are going to radiate light through Splits in a "wall" in different ways and observe the behaviour of the light-particles by checking how the light is projected on a canvas behind the splits. The double-slit experiment was performed originally by Thomas Young in 1801.
Experimental Setup
Radiating through single-split
First we are going to radiate through a single-split and watch our Canvas.
The result, when we close the left split, is a lightstripe on the right side of the canvas with decreasing intensity to its edges.
I would say that this is the result which most people would expect since it is comprehensibly. The same thing would happen if the light is radiated through the other split.
Radiating through double-split
Now lets radiate through both splits simultaneously and see what happens.
Now we can see a so called inteference pattern. This happens because light is moving in form of waves and waves have the characteristic that, when they intersect, they will either nullify or change the intensity of their frequence. It depends on where they are intersecting.
You can even try this by your own. The next time you are on a lake or a pond, try to create two waves next to each other and you´ll see that there will appear an interference pattern like in the following picture.
Well until here everything is more or less understandable and comprehensible but lets go further.
The question is:
What happens when we shoot single light particles (photons) through the splits?
Double-Split-Experiment (single photons)
The first thing we need to do is to change our "lightsource" we need something that can shoot single photons, lets call it a photoncanon. And the canvas now gets covered with a photo-sensitive foil so we can see where the photons impinge. The rest of the experimental setup remains as it was.
Shooting through single-split
In this case, the green area is the area inwhich the photon can possibly hit the canvas. That means if we shoot an infinit number of photons through the single split we would get the same pattern as we got whit the laser. Same would happen when only the split on the other side is opened.
Shooting through double-split
Lets open both splits and see what happens.
Again, the green area is the area inwhich the photon can possibly hit the canvas. That means even when we are shooting singe photons we are getting an interference pattern. But this should be impossible because the photon is not interacting with other photons.
So why is a single photon which is shot through the double split behaving like intersecting waves? It somehow moves through both splits but that also should be impossible.
Shooting through double-split while observing
Lets repeat what we just did but this time we are going to observe both splits to determin whether the photon is going through the left or right split.
This is the crazy part of the whole experiment. As soon as we are observing the splits and the photons we determine that the photon is allways going through one of the splits. Lets say every first goes through te left and evey second goes through the right split. That means the photons are forced to go through one of the splits when they are under observation so the pattern on the canvas is like we would expect. Fascinating!
Conclusion
What can we learn from this experiment? Can we change how our world is just by observing or not observing it? Are things as we think they are when no one is looking? Are they even existing? So many question occur when looking at this experiment and like i said this is just the tip of the iceberg.
Feel free to correct me if anything i said was wrong or to discuss this topic in the comments. Im looking forward to your reactions.