What is Bohr: Definition and 210 Discussions

Niels Henrik David Bohr (Danish: [ˈne̝ls ˈpoɐ̯ˀ]; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. Bohr was also a philosopher and a promoter of scientific research.
Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another. Although the Bohr model has been supplanted by other models, its underlying principles remain valid. He conceived the principle of complementarity: that items could be separately analysed in terms of contradictory properties, like behaving as a wave or a stream of particles. The notion of complementarity dominated Bohr's thinking in both science and philosophy.
Bohr founded the Institute of Theoretical Physics at the University of Copenhagen, now known as the Niels Bohr Institute, which opened in 1920. Bohr mentored and collaborated with physicists including Hans Kramers, Oskar Klein, George de Hevesy, and Werner Heisenberg. He predicted the existence of a new zirconium-like element, which was named hafnium, after the Latin name for Copenhagen, where it was discovered. Later, the element bohrium was named after him.
During the 1930s Bohr helped refugees from Nazism. After Denmark was occupied by the Germans, he had a famous meeting with Heisenberg, who had become the head of the German nuclear weapon project. In September 1943 word reached Bohr that he was about to be arrested by the Germans, and he fled to Sweden. From there, he was flown to Britain, where he joined the British Tube Alloys nuclear weapons project, and was part of the British mission to the Manhattan Project. After the war, Bohr called for international cooperation on nuclear energy. He was involved with the establishment of CERN and the Research Establishment Risø of the Danish Atomic Energy Commission and became the first chairman of the Nordic Institute for Theoretical Physics in 1957.

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  1. I

    Cyclotron magnetic dipole moment

    Hello, this is a question regarding Penning trap design. I need to calculate the magnetic dipole moment of the cyclotron motion, as a function of the cyclotron quantum number. The result needs to be given in terms of Bohr's magnetron. The magnetic dipole moment is defined as current x area...
  2. bhobba

    I Interestingly Bohr Did Not Believe in Wavefunction Collapse

    I was reading an article 'What Einstein Really Thought about Quantum Mechanics' in Scientific American. There they mentioned something I didn't know - Bohr did not believe in Wave Function Collapse as an issue (I don't either - but that's just my opinion, so means nothing). I found this...
  3. D

    Estimating the Bohr radius from the uncertainty principle

    Soo. I think this problem is too direct and easy so I think I got it in wrong way: p=h/r and then plug in the K and V and then we get E=E(r) and get derivative and we have minimum? What do you think? is there sth I am missing?
  4. S

    Bohr radius of Earth-Sun system

    When I looked up for Bohr radius, the formula has ##q## in it, which is charge of the object. For this question, the electron and proton are replaced by sun and Earth so it means that I have to know the charge of Earth and sun? Thanks
  5. A

    I Question about the Bohr model of atom and and electron in an orbital

    I have a question about what happen when an electron in the Bohr model of atom, gains energy because for example is "hitting" by a photon. Electron have an energy, and it is the sum of potential and kinetic. When they gain energy, they gain potential energy so they go further away from nucleus...
  6. docnet

    How Much Energy is Released When a Uranium Nucleus Captures an Electron?

    A neutral uranium atom has 92 electrons and 92 protons. in a violent nuuclear event a uranium nucleus is stripped of all 92 electrons. The resulting bare nucleus captures a single free electron from the surroundings. Given that the ionization energy for hydrogen is ##13.6eV##, derive the...
  7. D

    Calculate electric polarizability

    Hello everyone, I've got my non-uniform electric cloud distribution formula given by: ## \rho(r) = \frac {-Ze} {\pi a^3} e^{-{2r}/a}## Where ##Z## is the atomic number of the atom in question and ##a## Bohr's radius and ##E_L## the local electric field. Considering the previus expression ...
  8. F

    Bohr Model - Absorbing a Photon with Enough Energy to Ionize the Atom

    I just want to confirm something. You need about 13.6 eV of energy to ionize a hydrogen atom in the ground state. Can the atom absorb a photon with 15 eV of energy? I think it can. This would free the electron, and the freed electron would move off with a kinetic energy of 15 minus 13.6 eV...
  9. S

    Solving Bohr Atom Problem (Qs a-e)

    Hello folks, I've managed questions (a) and (b) but don't get what to do with part (c). Normally you would equate the velocity equations v2=e2/4πεmr=(n2h2)/(m2r2 ). This let's you isolate the radius and use it to calculate En. But I can't see how you could do this for v given in (a) and (b)...
  10. bhobba

    I Have We Got What Bohr Thought Wrong

    Feynman once said something along the lines of that when scientists talk about the history of science its a version handed down to them by their science teachers or from science textbooks. This may not be the same as what a professional historian of science says. As an example of this see the...
  11. bhobba

    I Is Entanglement Properly Defined in Bohr's Idea of Complementarity?

    I was reading an interesting article on the Bohr/Einstein debates. Interestingly it got most things right including the real reason Einstein thought QM incomplete - its not the probabilistic nature - it was that it didn't gel with his intuition on how nature works having features like...
  12. I

    I Bohr model for electron energy states

    I know that we use quantum mechanic and wave function to calculate probability of finding electrons but is there anything valid about bohr model that we still use it?
  13. Vividly

    I Einstein & Bohr Debate: Epistemological Paradox

    Im reading a book called “Quantum” the deabate between Einstien and Bohr. I’ve read reviews on it and this one particular review said the book doen’t delve into the “epistimological paradox” theat caused the two debaters to take their stand in their arguement. My question is, what was their...
  14. J

    B Bohr's Views on Relativity: What Did He Think?

    We hear a lot of Einstein on quantum physics. Did Bohr ever say what he thought of relativity?
  15. PGaccount

    I Understanding Bohr's Theory: Spacetime & Energy Momentum Relations Explained

    The spacetime and energy momentum relations can be written as t2 - x2 = s2 P+P- = m2 Niels Bohr says that "the spacetime or energy momentum relations must be applied at least twice, otherwise they are not defined". Does anyone know what he means by this?
  16. jedishrfu

    B Pilot-wave is No More, Pilot-wave cracked by Bohr

    Pilot wave Quantum Mechanics is doomed from recent experiments but wait there's more: https://www.quantamagazine.org/famous-experiment-dooms-pilot-wave-alternative-to-quantum-weirdness-20181011/
  17. W

    B Who drew the first model of the atom?

    Does anybody know who first drew (not just described but actually drew, even roughly) a model of the atom like the one below, and when: I'd appreciate it if anybody can point me to an evidence.
  18. Giulio Prisco

    I Einstein-Bohr "photon box" debate and general relativity

    I see this has been already discussed but the old threads are closed. EPR before EPR: a 1930 Einstein-Bohr thought experiment revisited "In this example, Einstein presents a paradox in QM suggesting that QM is inconsistent, while Bohr attempts to save consistency of QM by combining QM with the...
  19. Sahar ali

    I When Should the Bohr Atom Behave Classically?

    under what condition should the Bohr atom behave classically?
  20. T

    Rutherford model of atom and Bohr model

    Homework Statement Question a) Briefly describe the Rutherford model of the hydrogen atom and mention any inadequacies that it might have. b) Describe the Bohr model of the hydrogen atom, and indicate the significance of the quantum number 'n' in the Bohr model. Homework EquationsThe Attempt...
  21. J

    Bohr Model Modifications into the Rutherford Model

    Good afternoon. Which modifications did the Bohr model introduce into the Rutherford one to justify the Discountinuous atomic spectra, specially the one for the Hydrogen atom? Thanks
  22. Christina Lin

    Compare and contrast Bohr and Feynman?

    While doing research on Feynman and Bohr, I came across how Bohr never warmed up to Feynman even though he frequently sought him out for discussions in Los Alamos - which lead me to this question. Reasons were given for why he may not have, but that still leaves me wondering if there was...
  23. learis

    B Where Can I find the Einstein vs. Bohr Full Debates

    I've tried every way google searching to find the actual einstein bohr debates. But it's basically just commentary and summaries on them. I want to actually read the debates word for word, as well as any other dialogue the two had between them that was made public. Does anyone have any sources?
  24. S

    Bohr orbit (extremely confused)

    Homework Statement Calculate energy of electron in first excited state of hydrogen atom. Homework Equations n=2 when i use E=-13.6 (z/n)^2 and then use E=hc/lamda(wavelength) then wavelength is coming wrong The Attempt at a Solution the correct answer is 6.68 armstrong.
  25. P

    B Question on the Bohr atomic model and energy

    Let's say there are three states ofor energym, E1, E2 and E3, and the electron is at E1, what happens if a photon has energy E > E2-E1 ? Does it interact to the electron anD take it to E2 and the photon loose energy E2-E1 or it doesn't interact at ALL? I mean, the electron can't have an energy...
  26. H

    B Some website about new Bohr model

    This website <link removed> by some Japanese guy talks about a new Bohr model that can accurately calculate energy of Helium and other noble gases, as well as bonds, in non-relativistic level. (I happened to come across this website when I was searching about spinor.) He also reviews why old...
  27. ChrisisC

    B Science behind Einstein vs. Bohr Debate?

    On a episode of "PBS Spacetime" (fantastic youtube series, go check it out), the host mentioned that Bohr believed that reality doesn't exist until a quantum system is observed. Einstein believed that the universe still runs independently outside of a conscious observers mind. What is the actual...
  28. bluejay27

    I Exciton Bohr Radius: What is It & Why Does it Matter?

    What is the exciton Bohr radius? I understand that the exciton is the paired distance of an electron and hole. How does the Bohr radius play a role in this?
  29. K

    I Bohr model, Why do we assume a standing wave?

    Hi, I wonder why we assume the matter wave of an electron is standing wave. Is there any reason why it has to be standing wave?Is it because standing wave is the right "wave equation solution" that satisfies integer multiple behaviour of bohr model?
  30. J

    B Why did Bohr & Company hold quantum reality to be indeterminate?

    QM declares reality to be inherently indeterminate. Another hypothesis is that it is in fact determinate, but due to measurement uncertainty appears to be indeterminate. Why did Bohr, Heisenberg & Co adopt the first hypothesis and reject the equally valid second, when the two are experimentally...
  31. adamaero

    Bohr Model applied to Excitons

    An exciton is a bound electron-hole pair (in a semiconductor). For this problem, think of an exciton as a hydrogen-like atom, with a negatively charged electron and positively charged hole orbiting each other. The permittivity of free space (ε0) is replaced with permittivity of the...
  32. Vitani11

    How do you modify the Bohr model equation for Li++?

    Homework Statement Consider an electron in the n = 4 level of Li ++. According to the Bohr model, what is the radius of the orbit of the electron? Homework Equations r = .0529 nm r(n) = (.0529 nm) x (n2) The Attempt at a Solution I thought this was pretty obvious? We want to know the radius...
  33. K

    I Why the energy inversely propotional to n^2 in Bohr model

    After reading some materials on Bohr model, I understand the model is more or less incorrect, especially in terms of "orbital". I just wonder if the energy expression is also wrong or not. In my text for general quantum theory, the energy about two neighboring level is given as ##\Delta E =...
  34. V

    Bohr frequency of an expectation value?

    Homework Statement Consider a two-state system with a Hamiltonian defined as \begin{bmatrix} E_1 &0 \\ 0 & E_2 \end{bmatrix} Another observable, ##A##, is given (in the same basis) by \begin{bmatrix} 0 &a \\ a & 0 \end{bmatrix} where ##a\in\mathbb{R}^+##. The initial state of the system...
  35. epenguin

    Elements of truth - Moseley, Bohr, recognition and teaching.

    There is no longer a history section in PDF, but this is not suitable for any speciality forum. Just yesterday*, as usual a step ahead and with uncanny prescience, I was recommending a student to familiarise himself with Moseley's law as reinforcement and more in the learning of atomic physics...
  36. adfreeman

    B Bohr vs Einstein: is the Moon there when we are not looking?

    For some time now I’ve been intrigued by the famous argument between Bohr and Einstein, and which was apparently settled when Bell’s inequality was tested in various experiments carried out by Alain Aspect. After going around and around the whole issue for a while, I don’t think I’m convinced...
  37. 1

    Calculate Bohr Radius of Hydrogen Atom (n=600)

    I'm doing a homework problem where it asks to calculate the diameter of a hydrogen atom with n=600. I used the equation $$r=\frac{n^2a_0}{Z}$$ where $$a_0=0.529e^{-10}m$$. Solving for r yields: $$r=\frac{(600^2)(0.529e^{-10}m)}{1}=1.90e^{-5}m$$ Multiplying by 2 to get the diameter yields...
  38. C

    Electric Potential and Ionization Energy of Bohr Hydrogen

    I was studying for (first year) physics class and was playing around with the Bohr Model of Hydrogen. I tried calculating the electric potential at the Bohr radius r =5.29e-11 m, where V = \frac{e}{4 \pi \epsilon_0 r} (from the point-charge formula for electric potential) and I got 27.19 J/C...
  39. M

    Does the Bohr model go against classical Electromagnetism

    I was told in high school that Rutherford's atomic model was wrong because an electron which is in acceleration must release energy. That's how electromagnetic waves are made. and then I was told that Bohr gave his model and solved this problem. By making energy quantized. But what I really...
  40. E

    Bohr model and relativistic electron mass

    From the semi-classical Bohr model of the hydrogen atom the velocity of the electron in a certain orbit can be determined. With these velocities the electron's relativistic masses can be determined. With E=mc2 the energy levels are in agreement with those from the Bohr model. I know Bohr's model...
  41. Rapier

    Quantum Theory of Earth Satellite Analogy to Bohr Model

    Problem: In analogy to the Bohr Theory of the hydrogen atom, develop a quantum theory of Earth satellites, obtaining expressions for the orbit radius (r) and the energy (E) in terms of the quantum number (n) and the other relevant parameters. A satellite of mass 1000 kg is in a circular orbit of...
  42. squelch

    The Bohr Radius and reduced mass

    Homework Statement A muon is a particle with a charge equal to that of an electron and a mass equal to 207 times the mass of an electron. What is the radius and energy of the ground state of hydrogen if the electron is replaced with a muon? Don't forget to use the concept of reduced mass...
  43. F

    Calculating Bohr Magneton: Need Help with Unit Conversion

    Hi everybody; I am triying to calculate the Bohr Magneton (eħ/2mc); I am suposed to express it in units of MeV/ Gauss, but I have not idea how to transform charge/time, which is what I obtain when I introduce the units in the formula. Can anyone help plase? Thanks.
  44. T

    Magnetic Dipole less than that of the Bohr Magneton

    Hey there, The basic unit for magnetic dipoles is the bohr magneton μB = e ħ / 2 me Is it possible to have a magnetic dipole moment of a fraction of a bohr magneton, say, 0.5 μB Is it possible because the mp of a proton is greater than that of an electron, so following the same formula, its...
  45. K

    Electron revolutions in Bohr model

    Homework Statement On the average, a hydrogen atom will exist in an excited state for about 10-8 s before making a transition to a lower energy state. About how many revolutions does an electron in the n = 2 state make in 10^-8 s? Homework Equations L = mvr = Iω = nħ rn = n2a0/Z The Attempt...
  46. A

    Bohr Quantization with linear potential

    Homework Statement Using Bohr's quantization rule find the energy levels for a particle in the potential: $$U(x) = \alpha\left|x\right|, \alpha > 0.$$ Homework Equations ##\oint p\, dx = 2\pi\hbar (n + \frac{1}{2})## The Attempt at a Solution Okay so: ##\begin{eqnarray} \oint p\, dx &= \int...
  47. J

    Understanding the Bohr Model and Electron Decay

    Hi, I'm really struggling to comprehend how the Bohr model solves the problem of accelerating electrons losing energy and decaying into the nucleus. I've read through a lot of discussions on line and on PF and all I keep on reading is stuff like, the quantization of energy levels leads to a...
  48. Ganesh Ujwal

    What is the potential field of an ion near the Bohr radius?

    I figure that at large enough distances, the potential field of an ion is just the Coulomb potential for its net charge. But what happens at scales comparable to the ion's Bohr radius? Could there be, for example, some sort of screening effect from the electron shell that changes the potential...
  49. J

    Experiment from Einstein Bohr debate

    I was wondering if anyone could comment on this experiment: https://www.atom.uni-frankfurt.de/publications/files/Schmidt2013PRL.pdf, which supposedly experimentally realized Einstein's thought-experimental objection to Bohr at the Fifth Solvay International Conference on Electrons and Photons in...