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Double-slit experiment

The nature of light: wave or corpuscles?

Double-slit experiment
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The double-slit experiment was invented in 1801 by Thomas Young to study the nature of light. Young was convinced that light behaved like a wave, while other scientists, such as Isaac Newton, preferred to think of it as composed of corpuscles (= light particles).

Young decided to pass a beam of light through two small slits in an opaque screen, behind which he placed a white surface.

double slit

Young observed a series of stripes appearing on the white surface behind the slits, rather than a set of circular spots corresponding to particles passing through the two slits.

interference

The series of bright and dark stripes observed by Young corresponds to the diffraction pattern, which was described in the article about diffraction

In this way, he demonstrated that, in this case, light behaves like a wave.

After this experiment, Isaac Newton's idea of imagining light as a collection of particles was completely abandoned, but it was later revived by Einstein in 1905 to explain the photoelectric effect described in Book 3.


Young's experiment was used much later with electron beams and produced the same diffraction patterns as the original experiment conducted with light. Read more in the article Discovery of the electron as a wave.

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