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When Light Behaves as Waves and Particles

Updated: Jun 18, 2021

Author: Ellie Wang

Editors: Vincent Chang and Kira Tian

Artists: Cici Zhang

The double-slit interference experiment of a single particle, an experiment that proves the wave-particle duality of light, is one that’s shocking. When a beam of light passes through the first slit, it breaks up. Then, it passes through the next two slits like two water waves. The encounter forms account interference, which proves that photons are volatile.

Scientists wondered what would happen if, according to classical physical principles, the light particles in this experiment passed through the first slit and then through the double slit. Each light particle should pass through the first slit one by one like a bullet, then it should pass through one of the double slits and leave two slits on the backlight screen corresponding to the two rays. But interference is still occurring when light particles pass through the double slits one-by-one. The explanation from scientists is that a single photon passes through the two slits at the same time and interferes with itself. The fact that a microscopic particle can appear in two different places at the same time while also having an impact surprised the science community.

The distance between the double slits is also incredibly long. After De Broglie proposed that matter also has volatility, scientists found that a single single-celled organism can perform a double-slit interference experiment. In the double-slit experiment, scientists used clever methods to detect which of the two slits the particle passed through first. However, once it became possible to measure which slit the particle passed through, the interference disappeared. But if the measurement was erased, the particle passed through uncertainty again and its interference reappeared. It was almost like microscopic particles deliberately preventing scientists from discovering their secrets!

It is unfathomable as to whether the macroscopic world is made up of these microscopic particles, and it is also unclear whether the macroscopic world can also exhibit the uncertainty and wave-particle duality of microscopic particles under certain circumstances. Much like this uncertainty, there are so many other secrets in the world waiting to be unearthed.



Physics in a minute: The double slit experiment Electrons do not need to be Permalink

Submitted by Marianne on October 4

Francis, Matthew. “What Does the New Double-Slit Experiment Actually Show?” Scientific

American Blog Network, Scientific American, 7 June 2011,

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