The double-slit experiment is a famous experiment in quantum physics that demonstrates the wave-particle duality of matter and the observer effect. Here's a simplified explanation:
In the double-slit experiment, imagine a screen with two narrow slits. Behind the screen, there is a light source that emits particles, such as electrons or photons. These particles can behave both as waves and particles, and the experiment shows this dual nature.
When the particles are sent through the double slits, they can pass through either one of the slits or both simultaneously. On a screen placed behind the double slits, an interference pattern appears, similar to what you would expect when waves pass through two slits and interfere with each other.
This interference pattern suggests that the particles are behaving like waves, as waves exhibit interference patterns. However, when individual particles are observed or detected as they pass through the slits, something interesting happens—the interference pattern disappears. Instead, the particles behave as individual particles and create two distinct bands on the screen behind the slits.
This phenomenon is known as the observer effect. The act of observing or measuring the particles' path collapses their wave-like behavior into a definite position, removing the interference pattern. The particles are then detected as localized particles, similar to tiny bullets hitting the screen.
In essence, the double-slit experiment shows that particles exhibit both wave-like and particle-like behavior. When not observed, they exhibit wave interference patterns. But when observed or measured, they behave like particles with definite positions.
The interpretation of this experiment and its implications are still topics of ongoing discussion and debate in quantum physics. It highlights the strange and non-intuitive nature of the quantum world, where particles can exist in multiple states simultaneously until they are observed or measured.