De Broglie relation - new student

In summary, the conversation discusses the De Broglie relation and the Photoelectric effect in relation to quantum mechanics. The possibility of four low-energy photons having the same effect as one high-energy photon is questioned, but it is explained that this is not possible due to the lack of a mechanism for the electron orbital to store the energy. The concept of multiphoton processes is also mentioned, with the reminder that they only occur at high intensities. The conversation ends with a thank you for clarifying the topic.
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Hi physics folk,

Thought you guys would be able to clarify something, self study learner here getting into quantum.
So I've just learned about the De Broglie relation and The Photoelectric effect and am bamboozled (in a good way).

The notion being that light is absorbed in packets. However I'm unclear on this, if E = hf, surely you could arrange four photons (each with 1/4 of the excitation energy of the electron) so they overlap perfectly on the electron and thus excite it, or is it literally impossible in any scenario?

Also I was thinking about whether this quantum property is intrinsic to light. If you have an atom moving relative to an observer at 0.5c, away from a beam of photons shining on the atom, then the observer notes that the moving atom sees a frequency given by the classic doppler shift, e.g. Photons with a lower frequency.

Meanwhile in the atom's frame it notes a different frequency, given by the special relativistic doppler shift. That is, the two disagree on the photons striking the electron.

However if we add the time dilation factor to the observer frame the agreement is of course perfect. However does this not indicate that the wave packet energy is not intrinsic to the wave, that is waves of a different frequency can appear to create the same excitation?
 
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  • #2
In order for 4 low-energy photons to create the same effect as 1 hi-energy photon, the electron orbital would have to have some way of storing the energy - even for only a femtosecond. No such mechanism exists.

As for your second question: it's all about the available energy. So what counts is what the atom sees. If we see a low-energy photon, but it sees a high-energy one, that higher energy will be available to the electron.
 
  • #3
mainguy said:
The notion being that light is absorbed in packets. However I'm unclear on this, if E = hf, surely you could arrange four photons (each with 1/4 of the excitation energy of the electron) so they overlap perfectly on the electron and thus excite it, or is it literally impossible in any scenario?
Multiphoton processes are indeed possible, see https://en.wikipedia.org/wiki/Two-photon_absorption. Such effects belong to non-linear optics and occur only at sufficiently high intensities.
 
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What is the De Broglie relation?

The De Broglie relation is a fundamental concept in quantum mechanics, which states that all particles have both wave-like and particle-like properties. It relates the wavelength of a particle to its momentum, and is expressed as λ = h/p, where λ is the wavelength, h is Planck's constant, and p is the momentum of the particle.

Who discovered the De Broglie relation?

The De Broglie relation was first proposed by French physicist Louis de Broglie in 1924. He theorized that if light could have wave-like properties, then particles such as electrons could also exhibit wave-like behavior.

What is the significance of the De Broglie relation?

The De Broglie relation is significant because it provides a way to understand the wave-particle duality of matter. It helped scientists to better understand the behavior of particles at the atomic and subatomic level, and paved the way for further developments in quantum mechanics.

How is the De Broglie relation applied in modern science?

The De Broglie relation has many practical applications in modern science, particularly in fields such as quantum mechanics, nuclear physics, and solid-state physics. It is also used in technologies such as electron microscopy, particle accelerators, and quantum computing.

Is the De Broglie relation limited to a specific type of particle?

No, the De Broglie relation applies to all particles, including electrons, protons, neutrons, and even larger particles like atoms and molecules. It is a fundamental principle of quantum mechanics that applies to all types of matter.

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