Double slit experiment: the experiment simply explained

In quantum physics, the double-slit experiment provides an explanation for so-called interference patterns - and thereby questions our understanding of reality. We explain in a simple and understandable manner what is behind it.

The basis for the double slit experiment

The starting point for the experiment is Isaac Newton's assumption that light is a stream of particles. He justified this thesis in 1703 by the fact that light propagates along straight lines at high speed and reflects predictably on a mirror surface.

• 100 years later, Thomas Young would like to use an experiment to prove that light travels in waves. And moreover, when you bend over obstacles, that is, move on in new, smaller waves.
• Circular wave patterns are created at obstacles where the light is deflected.

This is how the double slit experiment works

The double slit experiment consists of a light beam, an obstacle with two slits and a screen.

• The light is shone on the obstacle.
• Thereupon the light beam breaks at the columns and two waves arise which continue to radiate from the respective columns.
• The screen behind the columns catches the light. The interference pattern is now located there.
• This pattern not only shows two bright stripes (right where the light shines through the obstacle), but there are several streaks of light on it.
• The reason: The two curved waves overlap on the way to the screen. These overlaps are bundled and there are also bright areas between and next to the immediate light strips.

The interference pattern was not the only discovery

But that's not all: the experiment was repeated with a kind of electron gun. Instead of a light beam, individual electrons are fired in order to avoid an interaction.

• In this case, a different result was expected. Similar to a real rifle that you shoot at a wall with two columns, you expect exactly two stripes on the other side.
• Namely, only exactly where the balls - in the experiment the electrons - pass through the gaps. However, an interference pattern was also formed here.
• In order to find an explanation for this phenomenon, sensors were attached to the columns in the next step to understand the behavior of the electrons.
• But when the scientists started the experiment, there was no interference pattern, but the previously suspected two strips of light.
• Accordingly, the behavior of the electrons changed after the detectors were installed. In other words, the electrons changed their behavior after installing detectors.

This is how physics tries to explain the result

It was this experiment that raised some questions and gave many interpretations. One of the theories explains the phenomenon as follows:

• It is assumed that the basis for reality and matter is only virtual. We actually live in a virtual reality, so to speak.
• Atoms, the building blocks of everything that exists, consist of 99.9 percent empty space. And the atomic nucleus also consists almost entirely of empty space.
• If you now refer to matter itself, which consists of atoms, which in turn consist of 99.9 percent empty space, only the information about this matter remains as a consequence. Because the closer you look at something, the less is left.
• Knowledge of matter in this model is therefore more important than matter itself.

Another explanation of the model

This model could also be explained as follows:

• Consider a canvas behind which a person uses light to cast shadows on the canvas.
• So you only see the shadow of the object, the projection. In this reality, only the shadow exists.
• The actual object is therefore only available to you in the form of information. Namely outside of your reality.
• This model now states that matter is only present when a viewer looks at it. The object is only "rendered" when someone looks at it.
• As soon as you turn away from an object, the "rendered" version is no longer required, only the information about the matter remains.

Quantum physics explains the phenomenon differently

In quantum physics one speaks of probability distribution. At first there is only information about the electron. It does not really fly an electron towards the gap, but only a cloud of possible probabilities for its actual position.

• The exact position of the electron is therefore still undetermined. Only if you measure exactly, it has an actual position.
• After the detectors are attached to the slit, the probability cloud disappears and the electron gets an exact position.
• Exactly two strips of light appear on the screen.
• Without detectors, two clouds fly through the column from possible positions, interact with each other and the interference pattern is created.
• The double slit experiment thus provides the basis for a different understanding of matter and that our reality may be completely different than previously thought.

Many physical experiments are carried out in Cern in the particle accelerator. We'll explain what it's all about.

$config[ads_text5] not found