How can light behave like a wave

Quantum object electron

Waves or particles?

according to R. Sexl: Matter in space and time

There are experiments with both light and electron beams, some of which can be explained more clearly with the wave model, the other with the particle model. But what is light or electron radiation really? Wave or particle? A physicist formulated this dilemma for light almost resignedly: "On Monday, Wednesday and Friday the light is a wave, Tuesday, Thursday and Saturday it is a particle and on Sunday it rests."

In his book "Matter in Space and Time", Roman Sexl lists various approaches as to how one could cope with the dilemma:

  • There are contradictions in nature that one has to live with. The contradicting wave properties and particle properties are examples of this.

This somewhat fatalistic approach is not pursued any further. It is more plausible to look for contradictions in our theories about nature than in nature itself.

  • It is useful to sometimes prefer one model and sometimes the other. Other models may be necessary to explain other phenomena.

This unrelated juxtaposition of models that are not combined into a unit by a superordinate theory will not be pursued any further.

  • There is a superordinate theory (quantum physics) which is suitable for describing the elements of the micro-world (quantum objects). The terms wave and particle are based on our “macroscopic” experience. Neither our senses nor our language can adequately grasp the micro-world. The very indistinguishable, strongly mathematically oriented and meanwhile extremely successful quantum theory cannot be mastered with the mathematical means available to us. In the sense of the curriculum, however, a little insight into the world of thought of quantum physics should be attempted at this level.

In this context, the famous physicist and Nobel Prize winner Richard FEYNMAN should be quoted:
In very small dimensions things behave like nothing of which we have direct experience. They don't behave like waves, not like particles. . . or anything we've ever seen.

The picture of modern physics is largely determined by quantum theory. That even great physicists had bigger problems with this theory (at least initially) is shown by the following quotes, which are somewhat comforting for us "normal consumers".

Albert Einstein (1879-1955):
  • 1917 - The rest of my life I will think about what light is!
  • 1951 - Fifty years of intense reflection gave me the answer "What is light?" not brought closer.
  • In a letter to Max Born about the probability statements of quantum physics: "The theory delivers a lot, but it doesn't bring us any closer to the mystery of the old (God). In any case, I am convinced that he does not roll the dice.

Richard FEYNMAN (1918 - 1988)

  • I think I can assume that no one understands quantum mechanics.
  • “There was a time when newspapers said only twelve people understood them theory of relativity. I don't think there was ever such a time. On the other hand, I think it's safe to say no one understands Quantum mechanics.“

Max BORN (1882 - 1970)

Nobel laureate Born wrote in a letter to Einstein: "The quanta are a hopeless mess."

Niels BOHR (1885 - 1962)

"When Einstein sends me a radio telegram that he has now finally proven the particle nature of light, the telegram only arrives because the light is a wave."

Illustrations on this page:

Albert EINSTEIN: by Ferdinand Schmutzer [Public domain], via Wikimedia Commons
Richard FEYNMAN: By Copyright Tamiko Thiel 1984 (OTRS communication from photographer) [CC-BY-SA-3.0], via Wikimedia Commons
Max BORN: from Unknown [Public Domain], via Wikimedia Commons
Niels BOHR: from unknown ( [Public domain], via Wikimedia Commons