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. P

    Bohr Model and wave-particle duality

    I am currently studying wave-particle duality. However, at the moment I do not see how the Bohr Model is connected to this topic. I know that the Bohr Model failed to recognise various aspects of the atom and that it works only for single atoms e.g. Hydrogen, but what did it fail to do when it...
  2. G

    Landau levels and bohr model

    hi i thought that if i try to derive the energy of an electron in a magnetic field, this could be done with the assumptions of the bohr model. L=n h/(2π) mv²/r=qvB => mvr=qBr²=>n h/(2π)=qBr² E=p²/(2m)=q²B²r²/(2m)=n h/(2π)qB/(2m) so i get the energy for the first level, but all transitions...
  3. B

    How did Niels Bohr obtain ΔT •ΔE > h?

    I mean when I deduct the Einstein’s box Bohr designed , I can not obtain the ΔT •ΔE > h like Bohr. 1) After balancing, the position of the spring-balance in weighing the box at the time 0 (T0) is Q0, and the weight of the box is M0. Because the experiment did not restrict the measuring...
  4. C

    Feynman is more important than Bohr

    I would challenge the tradition of viewing Bohr as the most important quantum physicist. I think all of the modern physics, in a nutshell, is "relativistic quantum field theory". Thus, we need to choose between two people: the author of Lagrangian formulation OR the author of Hamiltonian one...
  5. B

    Correct way to calculate energy in Bohr Atom Model

    I was deriving Bohr model formulas and I stumbled upon a problem. When I use the postulate that says that you can apply Newtonian Mechanics to orbiting electron, I wrote the Coulomb's force as following: Fc=(-e)*Z*e/(4pi(epsilon0)*r^2) Minus from the electron means that the force...
  6. marcus

    Reminiscences: 1976 interview with J.A.Wheeler (friend of Bohr and Einstein)

    http://arxiv.org/abs/1105.4532 In case anyone is interested. John Archibald Wheeler was a a great 20th C physicist (he was Feynman's PhD advisor I think.) He had originality and vision. I'd like to have more links to online sources that have Wheeler remembering people and events of his...
  7. C

    Bohr Quantisation Question

    Homework Statement The ionisation energy of a single hydrogen atom is 13.6 eV. The application of Bohr quantisation to the hydrogen atom results in the stationary states having discrete energies given in terms of a positive integer n according to E=-RB/n2 where RB is the Rydberg...
  8. J

    Need Help Understanding Bohr Model Equations

    Bohr incorporates Plancks's quantum theory into his model, placing conditions on the value of the angular momentum. angular momentum = nh/2pi n=principal quantum number h= Planck's constant since its giving me the angular momentum, is it actually giving me a number that corresponds to...
  9. J

    The Bohr Model -answer one ? if not all

    hello, i am studying chemistry. There are a lot of things i do not understand though. This is not homework, just studies of my own that i would like to reach a deeper understand of. I love the responses i have read, so decided to make an account and learn from all you geniuses! Bohr model...
  10. B

    Bohr Model Postulates: Understand Discrete Angular Momentum Orbits

    Hello, I am interested if anybody knows, how did Bohr came to the conclusion that only discrete angular momentum orbits are stable? In other words, m*v*r=n*h/(2*pi) and how did de Broglie came to the same conclusion, just through another way 2*pi*r=n*h/(m*v) Thanks
  11. M

    De Broglie & Bohr: Electron Kinetic Energy Formula

    An electron around a hydrogen-atom, with radius r and length of circle a whole number, n, times wavelenght. This implies that 2*3,14*r=n*(wavelenght) I have read someplace that if you substitute the wavelenght with h/p, you can find the kinetic energy of an electron, which is the same as...
  12. R

    Even Real Particles don't exist Aage Bohr

    Maybe not only virtual particles don't truly exist (as believed by many physicists now). Real particles don't exist as well. According to Aage Bohr, the son of Neils Bohr, particles don't really exist. Nothing moved through the space between the emitter and detector in the double slit...
  13. A

    Reevaluating the Bohr Model of the Atom and Its Radiation Emission

    I think a problem with the bohr model of the atom was that if the electron was in orbit around the nucleus, it would keep emitting radiation of longer and longer wavelengths until it falls into nucleus. Why does an electron in orbit necessarily have to emit radiation?
  14. S

    Derivation of velocity in nth Bohr orbit

    Homework Statement (a) Derive an expression for the electron's speed in the nth Bohr model. (b) Prove that the orbit with highest speed is the n = 1 orbit,with v(1) = ke^2 / h compare this with the speed of light , and comment on the validity of ignoring relativity (as we did) in...
  15. H

    Validate Bohr Radius: Challenges Creating Metallic Hydrogen

    Creating metallic hydrogen has proved more difficult than expected. One explanation would be that the Bohr radius of Hydrogen is smaller than expected. Is there any other evidence of an error in Bohr radius predictions?
  16. A

    Bohr model find orbital radius for electron

    Homework Statement In the Bohr model, the electron is imagined to move in a circular orbit about a stationary proton. If the speed of the electron were 8.9e5 m/s, what would be the corresponding orbital radius? Homework Equations The Attempt at a SolutionFe=ma Fe=ma a=Fe/m (v^2)/r=(kqq/r)/m...
  17. D

    Bohr Radius and Ground State Energy

    Homework Statement Given the potential energy V(r)=-\frac{1}{4\pi \epsilon_0}\frac{e^2}{r} (where e is the unit charge), use the uncertainty principle \Delta x \Delta p \geq \hbar to find the Bohr radius r_B for a hydrogen atom and the ground state energy E_0. Hint: write down the kinetic...
  18. A

    What is the lowest gravitational Bohr radius in terms of light years?

    Homework Statement If the attractive forces between an electron and proton only due to gravity is F=(Gx Me x Mp)/r^2. What is the lowest gravitational Bohr radius? c=2.99799 x 10^8 m/s Me= 9.10939 x 10^-31 Mp=1.67262 x 10^-27 h= 1.05457 x 10^-34 G= 6.67259 x 10^-11 Nm^2/kg^2...
  19. A

    Dynamics of electron in Bohr Hydrogen atom

    1. Consider Bohr Hydrogen atom with counter-clockwise electron orbit in the xy plane with intial position r(0)=-a0y. The angular frequency of the orbit is w. Derive an expression for the position of electron at a later time t, r(t) in terms of a0 , w, t, x, and y. Homework Equations...
  20. L

    Understanding Orbitals and Energy Levels in the Bohr Model

    I'm sitting with Physics Handbook and I'm trying to recall how the make out the orbitals in the energy levels. Let's take a look at the first levels. n = 1 - sub-shell K Number of electrons = 2n^2 \Rightarrow 2 electrons. Number of electrons = l = 0,1... n-1 \Rightarrow l = 0. This is where I...
  21. S

    Why the discrepancy in muonic H Bohr radius? 285 fm or 256 fm?

    Some places say (including this paper) claim the bohr radius of muonic hydrogen is 285http://ethesis.unifr.ch/theses/downloads.php?file=LudhovaL.pdf Many more peer reviewed papers say it is 256 fm, or 255 fm though. (search for '256 fm muonic' in teh googlez). So who is right? And more...
  22. S

    Can anyone confirm the ground state Bohr radius for muonic hydrogen?

    Thanks in advance for anybody who is kind enough to help me. No this isn't for my homework. I am not even enrolled in school. I am doing some calculations for personal research. But I need to know the ground state radius of a muonic hydrogen atom to help prove my theory. I already know the...
  23. A

    The Hydrogen Atom (Schrodinger vs original Bohr theory)

    What quantities appear in both the Schrodinger approach and the original Bohr theory of a hydrogen atom? Also, in what ways do the two approaches differ? I'm not sure which quantities appear in both approaches. My guess would be that it has something to do with the energy levels and angular...
  24. fluidistic

    Calculating Probabilities for Ground State Hydrogen Atom

    Homework Statement The normalized wave-function corresponding to the ground state hydrogen atom has the form \Psi _0 = \frac{1}{\sqrt \pi} \cdot \frac{e^{-r/a_0}}{a_0 ^{3/2}} where a_0 is Bohr's radius. 1)Graph the density of probability to find the electron in a spherical edge between r and...
  25. R

    Bohr Model Vs. Shrodingers Mech. wave model

    Homework Statement In Chemistry class i was assigned a essay. This essay was comparing and contrasting the mechanical wave model to Bohrs model of an atom. some things i have now are Bohrs -Unreliable for finding electrons in orbits -Dense core with protons - Shrodingers -ability to predict...
  26. J

    Bohr Hypothesis: Proving Orbital Radius is Quantized

    Homework Statement Question: If we assume that an electron is bound to the nucleus (assume a H atom) in a circular orbit, then the Coulomb force is equal to the centripetal force: mv^2/r= ke^2/r^2 In the Bohr hypothesis, angular momentum, L = mvr is quantized as integer multiples of...
  27. J

    Electrons bound to the nucleus/ Bohr hypothosis

    Question: If we assume that an electron is bound to the nucleus (assume a H atom) in a circular orbit, then the Coulomb force is equal to the centripetal force: mv^2/r= ke^2/r^2 In the Bohr hypothesis, angular momentum, L = mvr is...
  28. fluidistic

    Modern physics, Bohr model of atom

    Homework Statement According to Bohr's atomic model, 1)Determine the allowed radius of the orbit of the electrons. Calculate the radius of the first orbit for the hydrogen atom. 2)Show that the energy of the electron is quantized. Calculate the energy corresponding to an electron on the first...
  29. Z

    Semiclassical Bohr quantization with a magnetic potential

    Homework Statement given the Hamiltonian in one dimension H= \frac{(p-eA)^{2}}{2m}+ V(x) use the Bohr-Sommerfeld quantization in one dimension to obtain n=n(E) Homework Equations Hamiltonian , quantization The Attempt at a Solution from the usual quantization algorithm in one dimension i...
  30. A

    About The Bohr Model of the Hydrogen Atom

    Homework Statement What energy (in eV) is required to remove the remaining electron from a singly ionized helium atom, He+ (Z = 2)? (a) 3.40 eV (c) 27.2 eV (e) 76.9 eV (b) 13.6 eV (d) 54.4 eV Homework Equations Ei - Ef = hf The Attempt at a Solution Ef: the 1st level Ei...
  31. J

    Bohr - Van Leeuwen theorem and the velocity distribution

    There is an interesting theorem in statistical physics which states that the thermodynamical quantities of the system of charged particles are not influenced by the magnetic field (even if it is nonuniform). Imagine we have many particles in a cubic container with dimensions a \times a \times a...
  32. C

    Bohr & Solipsism: Reality or Illusion?

    I wonder if Bohr QM point of view could be labeled as "solipsism" or even "Metaphysical solipsism". Any hint would be appreciated. I may be wrong at some point, so I would be glad to hear other opinions or corrections. According to Bohr (subjective Copenhagen interpretation of Quantum...
  33. L

    Earth-Sun System as Giant Hydrogen Atom: Bohr Atom Problem

    Consider the Earth-Sun system as a giant-sized hydrogen atom, the objects interacting, however, by the gravitation force. (a) What is the quantum number, according to Bohr Theory, for the Earth's orbit about the Sun? (b) If the Earth were to make a transition to the next lowest quantum state, by...
  34. D

    Bohr Model in Polar Co-ordinates

    The angular momentum of the Bohr atom is ⃗L = ⃗r× ⃗p Let the Oz axis of the unit vector ⃗uz be determined by the relation L = L⃗uz, in which L stands for the magnitude of the angular momentum vector ⃗L . (Basically L is in Positive z axis) We specify the position of the electron within its...
  35. M

    Bohr Model Electron Movement Question

    Homework Statement How does an electron get from an excited state (r = 4ao) to a ground state (r = ao) without being anywhere in between? Homework Equations The Attempt at a Solution My only attempt would be to say that it does exist between for a short time, and during that time it emits a...
  36. Shackleford

    The Bohr Model of the Hydrogen Atom

    A hydrogen atom in an excited state absorbs a photon of wavelength 434 nm. What were the initial and final states of the hydrogen atom? E = hf = Eu - El = 2.825 eV That's the difference in energy between the initial and final states.
  37. F

    Forgotten Greats: Tycho Brahe, Harald Bohr, & More

    not "greatest ever" but "greatest ever who nobody thinks of" or something like that. maybe tycho brahe isn't the best example, but he's still overshadowed by kepler or galileo i think. or how about harald bohr (neils' younger brother). anyway that's the idea.
  38. Doc Al

    Niels Bohr: The Gunslinger Scientist

    http://news.bbc.co.uk/today/hi/today/newsid_8493000/8493203.stm"
  39. S

    Calculating the Bohr radius or velocity of an excitons

    while doing some calculations such as calculating the Bohr radius or velocity of an excitons in semiconductors such as GaAs I didnt understand why is it allowed to use the static permittivity even though the electron and hole aren't as heavy and the spectra is measured at high frequencies such...
  40. J

    Classical Physics and the Bohr Model of Hydrogen Atom

    Homework Statement Classical physics applied to the bohr model of the hydrogen atom would predict that light could be emitted continuously, rather than in discrete chunks of energy. Transitions between what kinds of energy levels would come close to the classical viewpoint? A. Only levels...
  41. N

    Bohr Model (Lyman,Balmer,Paschen series)

    Homework Statement Determine the wavelengths of photons given off for the 3rd line in the Lyman series , the 2nd line in the Balmer series, and the 1st line in the Paschen series. The question is weird, I don't understand what the "line" mean... "1st line in the Paschen series " Is it mean ni...
  42. apeiron

    Why did they ignore Bohr?

    One of the curiosities of 20th century physics was that the complementarity principle was central to the QM revolution, yet physics only took heed of uncertainty. Why? Kote would certainly have an opinion. But here are some relevant snippets to remind others. Niels Bohr on the importance...
  43. J

    Calculating Electric Force in Bohr Model of Hydrogen Atom

    Homework Statement In the Bohr model of a hydrogen atom, what is the magnitude of the electric force exerted between the proton and the electron when the electron is in the n = 1 state? Homework Equations E= - 13.6 eV/ n^2 The Attempt at a Solution I simply...
  44. P

    Can the Bohr Model really prevent electron energy loss?

    Even though Bohr's model is defunct, one important element of it survived, namely the strictly quantized orbiting radii of electrons. Supposedly this mended the gaping flaw of Rutherford's model in that it predicted that electrons would no longer lose energy to photon emission thereby causing...
  45. N

    Bohr Correspondence Principle

    Homework Statement For a particle in a one-dimensional box of length a, I am attempting to find the probability that the particle will be located between 0 and a/4, in the limit of large quantum numbers. Homework Equations The Correspondence Principle states that quantum mechanical systems may...
  46. J

    Probability of finding electron inside bohr radius

    Homework Statement Consider an hydrogen atom in its ground state, what is the probability that the electron is found inside the Bohr Radius? Homework Equations The probability of finding the electron at bohr radius is maximum. but the probability over the range from 0 to bohr radius...
  47. M

    Bohr model hydrogen potential energy

    Homework Statement How do you find the potential energy of the hydrogen atom in n=11 state using Bohr model? express in eV Homework Equations I used U= -kZe^2/r The Attempt at a Solution =-8.99e9(1.6e-19)^2/5.29e^-11 =4.35e^-18J / 1.6e^-19 =-27.2eV
  48. K

    Quantum mechanics replacing bohr model

    do all of the electrons in an atom have to move up or down an energy level or is it just the valence electrons or what? is there one photon released per electron and are they all the same wavelength?
  49. R

    Calculate Potential Energy of Electron in Bohr Model

    How can I calculate the potential energy of the electron when we bring it from the infinity to the distance r?
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