What is De broglie: Definition and 272 Discussions

Louis Victor Pierre Raymond, 7th Duc de Broglie (, also US: , French: [də bʁɔj] or [də bʁœj] (listen); 15 August 1892 – 19 March 1987) was a French physicist and aristocrat who made groundbreaking contributions to quantum theory. In his 1924 PhD thesis, he postulated the wave nature of electrons and suggested that all matter has wave properties. This concept is known as the de Broglie hypothesis, an example of wave–particle duality, and forms a central part of the theory of quantum mechanics.
De Broglie won the Nobel Prize for Physics in 1929, after the wave-like behaviour of matter was first experimentally demonstrated in 1927.
The 1925 pilot-wave model, and the wave-like behaviour of particles discovered by de Broglie was used by Erwin Schrödinger in his formulation of wave mechanics. The pilot-wave model and interpretation was then abandoned, in favor of the quantum formalism, until 1952 when it was rediscovered and enhanced by David Bohm.Louis de Broglie was the sixteenth member elected to occupy seat 1 of the Académie française in 1944, and served as Perpetual Secretary of the French Academy of Sciences. De Broglie became the first high-level scientist to call for establishment of a multi-national laboratory, a proposal that led to the establishment of the European Organization for Nuclear Research (CERN).

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  1. A

    De Broglie Wavelength - Can a Person Move Slow Enough?

    Just a random thought: is it not possible for a person to move slow enough to have an observable de Broglie wavelength? For example a person moving at around 10^-30 m/s should have a wave nature that is very observable.
  2. A

    De Broglie wavelength problem

    Homework Statement By estimating the De Broglie wavelength and the inter-particle spacing, find whether the following systems of particles are degenerate: (i) a gas of neutrons in a neutron star with mass density 10^17 kg/m^3 at the temperature of 10^8K (ii)a gas of oxygen molecules at...
  3. jinksys

    Calculating De Broglie Wavelength from Kinetic Energy

    Homework Statement Show that the de Broglie wavelength of a particle of mass m and kinetic energy KE is given by \lambda = \frac{hc}{\sqrt{KE(KE + 2mc^2)}} Homework Equations The Attempt at a Solution I know: KE = {\gamma}mc^2 - mc^2 = pc - mc^2 But from here I am...
  4. S

    Deriving the De Broglie Wavelength

    E=mc^2 and E=hf. In Special Relativity, how can y=h/p be derived from E=hf?
  5. M

    De Broglie wavelength application: molecular vibrations?

    Homework Statement In his presentation of the de Broglie wavelength and the wave/particle duality, my quantum prof. has an exercise: "Find the de Broglie wavelength of a molecular vibration. Do quantum or classical laws apply?" Homework Equations wavelength = h/(momentum) ...
  6. C

    Energy of a proton using de broglie formula

    I am trying to help my son in his year 12 physics. I know very little of this can someone please assist. find in eV (electron volts) the energy of a proton with a de broglie wavelength of 40 pm (picometres) What would the correct formula be ? A good chance for me to learn as well ;)...
  7. D

    De Broglie wavelength and it's dependence of the frame of reference

    Hello, I've always wondered about the "relativity" of the De Broglie wavelength. The wavelength depends on the momentum of the specific thing we are observing, thus on different frames of reference(F.O.R from now on :P) we might get different answers. I have been looking through the web to...
  8. J

    Calculating the de Broglie Wavelength

    Homework Statement Calculate the de Broglie wavelength of an oxygen molecule (molecular mass 32)in air at room temperture. Homework Equations P = h/ \lambda P= mv E= hv = 1/2mv^{2} = P^{2}/(2m)The Attempt at a Solution hv = 1/2mv^{2} h = 1/2mv If v = P/m then h = mp/2m so p= 2h This...
  9. C

    Importance of de Broglie wavelength of matter

    I can work out the wavelengths fine, but I am unsure of the answer to the second part, any help would be much appreciated
  10. D

    De Broglie wavelengths and electron diffraction

    I am interested to know why in any description of electron diffraction apparatus they seem to suggest that the electrons need accelerating up to 5kV (or at least several kV) to show the electron diffraction rings, this seems to give a de Broglie wavelength of around 1.2 x 10^-11m whereas the...
  11. P

    De Broglie wavelength of a neutron

    Homework Statement What is the de Broglie wavelength of a neutron whose kinetic energy is equal to the average kinetic energy of a gas of neutrons at temperature T = 17 K? Homework Equations lambda = h/p = h/mv. The Attempt at a Solution Well first I tried taking the h =...
  12. P

    De Broglie wavelength question.

    Homework Statement Earth has the mass 6 · 10^24 kg and the orbit radius r = 1.5 · 10^11 m. (a) Compute its de Broglie wavelength. (b) Apply de Broglie quantization condition as in the case of the Hydrogen atom and compute the quantum number n for the orbit of Earth. (c) What is the...
  13. O

    De Broglie wavelength of particle of diameter X

    Homework Statement In an electrom microscope we wish to study paprticles of diameter about 0.10 µm (about 1000 times the size of a single atom). What should be the de Broglie wavelength of the electrons? Through what voltage should the electrons be accelerated to have that de Broglie...
  14. Z

    Comparing De Broglie Wavelength & Atom Separation in Helium Gas

    Homework Statement The atoms in a gas can be treated as classical particles if their de Broglie wavelength is much smaller than the average separation between the particles. Compare the average de Broglie wavelength and the average separation between atoms in a container of (monoatomic) helium...
  15. O

    De Broglie wavelength of an electron

    Homework Statement Find the de Broglie wavelength of an 8 MeV proton. Homework Equations y = h/p where y is the wavelength p = mv K = Eo/sqrt(1-v^2/c^2) where Eo is the rest mass and K is the kinetic energy The Attempt at a Solution I make the assumption that "an 8 MeV proton"...
  16. S

    What vibrates in De Broglie waves?

    Hi, I am very new to Quantum Physics. In every wave, something should oscillate. In water waves, water molecules oscillate. In electromagnetic waves, electric and magnetic fields oscillate. So what oscillates for a de broglie wave? Take a neutron as an example.
  17. P

    Question regarding de Broglie wavelength.

    Hi there, Is it possible if an object were to hypothetically gain enough momentum such that its de Broglie wavelength is equivalent to, say, some light in the visible spectrum, that the object would emit light? Thanks!
  18. S

    De Broglie hypothesis problem

    According to the de Broglie hypothesis, which of the following statements is applicable to the wavelength of a moving particle?
  19. O

    De Broglie wavelenght of Earth and Moon

    Hi, Could someone please crunch for me the de Broglie wavelenght (\lambda), frequency (f) and energy (E) of Earth at perihelion (30300m/s) and at aphelion (29300m/s) and mean (29800m/s) Here are the numbers and formulas: \lambda=h/p , f=E/h , p=m*v (momentum=mass*velocity) h - Planck's...
  20. E

    Calculating de Broglie Wavelengths of Rb Atom and Electron

    Homework Statement What is the de Broglie wavelength of a 10 microKelvin Rb atom? A 5000K electron? Homework Equations \lambda=\frac{h}{p} V=\sqrt{\frac{3KT}{m}} The Attempt at a Solution I used the velocity equation to find the velocity relating to temperature and mass. Then, as...
  21. S

    De Broglie Wavelength - How does this hold for slow objects?

    OK so you get to the matter wave equation 'lambda = h / p' using E=cp - which describes the energy for massless particles. I can understand this holding for when cp>>mc^2 , but not for when the mc^2 is comparible. Any help?
  22. J

    De Broglie wavelength (relativistic e-)

    Wavelength of an electron Homework Statement -Electron has 3.00 MeV (or 4.8*10^-13 Joules) -it's relativistic -finding λ. Homework Equations h=6.63*10^-34 λ=h/p (obviously) And I'm not sure if they're needed, but the relativistic eq's are: KE = mc^2/sqrt(1-(v/c)^2)...
  23. M

    De Broglie Wavelength Calculation given electron velocity

    Homework Statement an electron is moving at 2.5 x 105m/s. Find the electron's De Broglie Wavelength. Homework Equations De Broglie relates wavelength of electron waves to momentum of the electron by lambda = h/p where h is Planck's constant. The Attempt at a Solution given the...
  24. P

    De Broglie Formula Application

    Homework Statement Estimate the wavelength of a 30 keV electron. Homework Equations p = h/λ E = hf The Attempt at a Solution The electron has 30 keV of mass-energy. As it is acting as a particle-wave, E = hf, so f = E/h = 30,000x1.6x10^-19/6.3X10^-34 = 7.619x10^18 Hz Now, v =...
  25. P

    De Broglie Wavelength Equation

    Homework Statement What was the significance of the de Broglie equation? Homework Equations p = h/λ p = mv The Attempt at a Solution It says that not only do waves act as particles, transferring energy and momentum to matter only at localised points, but moving particles (e.g...
  26. D

    De Broglie and other Quantum Questions

    Hi, just some quantum physics questions. I've given them all a good go, the first two just require checking, but the rest I'm rather stuck on. They're the last questions in about 20 other ones, and my head now hurts. :( Any hints are very much appreciated! Homework Statement I firstly...
  27. M

    De broglie wavelength and energy

    Homework Statement The potential-energy function U(x) has the constant value U_0 in the interval 0 < x < L and is zero outside this interval. An electron is moving past this square barrier, but the energy of the electron is greater than the barrier height. If E= 6 U_0, what is the ratio...
  28. M

    De Broglie wavelength question

    Homework Statement In one of the classes, a recent experiment showing the interference of C60 molecules using a double slit apparatus was discussed. (a) If the average velocity of the C60 molecules is v= 200 m/s, calculate the De Broglie wavelength for a C60 molecule Homework Equations...
  29. G

    What is the de Broglie wavelength of this electron?

    Homework Statement What is the de Broglie wavelength of this electron? Given is 500 eV Homework Equations KE= 1/2 mv^2 1 eV=1.602x19^-19 J The Attempt at a Solution I converted the 500 eV to 8.01x10^-17 via the given conversion. Now I'm stuck.
  30. G

    De Broglie Wavelength Derivation

    In Classical Mechanics the derivative of Kinetic energy with respect to velocity is momentum, so I was wondering if this is valid: In this L is lambda or wavelength and h is Planck's Constant. E=hf, therefore E=h(v/L) This means that dE/dv=h/L.(h and L are constants and the derivative of...
  31. M

    Relativistic De Broglie wavelength

    Homework Statement De Broglie wavelength What is the De Broglie wavelength of the 1.0-TeV (1TeV=1012eV) protons (mpc2=938.3MeV) accelerated at the Fermilab Tevatron accelerator? These high-energy protons are needed to probe elementary particles [Hint: You need to use relativistic formula, but...
  32. F

    What Happens to the de Broglie Wavelength as Mass Approaches Infinity?

    If, in the expression for the de Broglie wavelength, we let m -> infinity, do we get the classical result for matter? de Broglie wavelength = h/mv so as m goes to infinity the de Broglie wavelength goes to 0. So does this mean that particles with larger mass don't display wavelike...
  33. U

    What is the Correct Proof for the de Broglie Equation?

    I saw a proof in a book for the de broglie equation which I thought was wrong. if l = lambda, so wavelength and then all other notation is standard they said: E=mc^2 E=hf therefore, mc^2=hf but for a photon, c=v so: mv^2=hf but mv=P so: Pv=hf and v=fl so: Pfl=hf...
  34. S

    Dispersion Relation of a De Broglie Wave

    Homework Statement Use the dispersion relation to find the group velocity v_group and phase velocity v_phase. Homework Equations omega(k) = [(hbar)k^2]/2m The Attempt at a Solution v_group = domega(k)/dk = [hbar]k/m = h/m lambda = p/m = v This isn't right. v_phase = omega...
  35. S

    De broglie wavelength and orbits

    Homework Statement If the be Broglie wavelength associated to the first orbit of the electron inside the atom of hydrogen is 62.4 nm, what is the wavelength associated to the fourth orbit? 1. 62.4 nm 2. 124.8 nm 3. 312 nm 4. 249.6 nm Homework Equations # of...
  36. B

    Argh - De Broglie and the wave equation

    This isn't a homework question, but something which has been bugging me. I can't figure it out. Maybe it's late, but it's probably a very stupid question If light shines onto a denser medium, the light slows down in this medium right? If the light slows down, then by the wave equation, v =...
  37. C

    Exploring the Minimum Radius of a Star: De Broglie Wavelength

    Homework Statement I am trying to describe the limit for the minimum radius of a star to first year university level students in order to describe the reason for the size of the Sun. I'm a bit confused by the critical density of the material in the star's core and how we know that the main...
  38. snoopies622

    Head-on Elastic Collision & Wave-Particle Duality: Is There Something Deeper?

    If a ball with mass m_1 moving at speed v strikes another ball of mass m_2 that is initially at rest in a head-on elastic collision, the speeds of the two balls after the collision are v_1 = v (\frac {m_1 - m_2}{m_1 + m_2}), v_2 = v (\frac {2 m_1}{m_1 + m_2}) respectively. If a wave...
  39. C

    De Broglie wavelength of 30keV electron

    Homework Statement The question is from Advanced Physics by Adams and Allday, section 8 Practice Exam Questions, question 30. Estimate the de Broglie wavelength of an electron that has been emitted thermionically in a vacuum from a filament and then accelerated through a p.d. of 30.0 kV...
  40. S

    De Broglie wavelength, velocity of electron

    Homework Statement Question 1) Calculate the de Broglie wavelength of a neutron (mn = 1.67493×10-27 kg) moving at one fiftieth of the speed of light (c/50). Question 2) Calculate the velocity of an electron (me = 9.10939×10-31 kg) having a de Broglie wavelength of 225.7 pm...
  41. W

    Where did the de Broglie waves go?

    As a beginner in quantum mechanics I have already lost my way on de Broglie waves. A free particle is a linear superposition of de Broglie waves and satisfies the Shroedinger equation with zero potential. Do the component de Broglies waves have physical meaning or are they mathematical...
  42. P

    Momentum and De Broglie Wavelength in Quantum Mechanics

    what does the momentum in de broglie wavelength signify? i mean how do u defien it...we can define the expectation in momentum but how do we define momentum for "quantum mechanincal" particles
  43. C

    De broglie wavelength and velocity

    The de broglie wavelength is h/p, where p is momentum, and hence mv, so wavelenght = h/ (mv). The mass is on the denominator, so a massive object, like a baseball, will have a small wavelength, beyond detection and we can ignore it. OK, so does the mass have to be moving to have a de broglie...
  44. G

    De Broglie Wavelength problem

    Homework Statement A 220lb fullback runs the 40-yd dash at a speed of 19.6 ± 0.1 mi/h. What is he de Broglie wavelength (in meters)? Homework Equations de Broglie Wavelength: λ=h/(mu), where λ=wavelenght, h=6.626 x 10^(-34) kgm^2)/s, m=mass (kg), and u= speed The Attempt at a...
  45. B

    De Broglie wavelength and atom penetration

    Homework Statement Calculate the de broglie wavelength (DBW) of an electron with kinetic energy 60 GeV. What percentage of an atom's diameter can it penetrate? Homework Equations DBW = h/p p=mv The Attempt at a Solution Basically I have an electron traveling at the...
  46. R

    De Broglie wavelength calculations

    I had a go at 2 Q's and wanted to make sure I'm doing this right. so here's the first one, and maybe if i went wrong with it I was going to redo the 2nd Q on my own. \lambda = h/p = h/mv (\sqrt{1-((v^2)/(c^2))}) so, an Alpha Particle traveling @ 2x106m/s (mass = 6.645x10-27 kg)...
  47. C

    Solve De Broglie Waves Homework

    Homework Statement Atoms are on the order of one Angstrom (A) or 10-10m in size while the diameter of the nucleus is approximately one hundred thousand times smaller. Let's pretend we have a "classical" atom where both the atom and its nucleus have a defined position and size. (This it...
  48. X

    De Broglie wavelength of an electron and speed

    Homework Statement An electron has a de Broglie wavelength of λ = 6.4e-10m. What is its speed? What voltage was needed to accelerate to this speed? Homework Equations v=h/mλ KE = 1/2mv^2 The Attempt at a Solution I already determined that the speed is 1.136e6 m/s. Finding the...
  49. B

    Trying to plot de Broglie standing wave.

    Does anyone know how to plot the electron standing wave around a nucleus in Cartesian coordinates? I have tried adding a sine/cosine function to the circle equation but the image does not look correct and I also don’t know how to increase the wave count when n > 1.
  50. redtree

    Probability amplitudes, de Broglie and Schrödinger

    What is the relationship between the "matter waves" described by de Broglie, the probability amplitude function and Schrödinger's wave equation? I've read the following: "The wavelengths postulated by de Broglie to be associated with the motions of particles are in reality the wavelengths...
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