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A Bohr/De-Broglie postulate

  1. Aug 25, 2016 #1
    From the Bohr/De Broglie postulate we have n λ = 2πr where λ is the De-Broglie wavelength , r is the radius corresponding to n and n is the quantum number.

    1. An electron in the state n=2 has more energy than that at n=1
    2. That implies that the De- Broglie wavelength associated with the electron should also decrease ?
    From the postulate..it is the other way i.e. the wavelength increases as the electron gains energy. How is this possible?.( I had assumed that wavelength decreases with energy)

    if we calculate the De-Broglie wavelengths from the postulate:

    for n=1 ; λ = 33 * 10^-11 m

    for n=2 ; λ = 66 * 10^-11 m

    does this mean that as the energy of the electron increases the corresponding De-Broglie wavelength increases?! may be i am missing something very basic here.

  2. jcsd
  3. Aug 25, 2016 #2


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  4. Aug 25, 2016 #3
    Bohr's condition, that the angular momentum is an integer multiple of h/2.pi was later reinterpreted in 1924 by de Broglie as a standing wave condition: the electron is described by a wave and a whole number of wavelengths must fit along the circumference of the electron's orbit:

    however the atom model is bound state model and in each orbit the particles total energy must be negative (sum of KE + PE) and the lowest orbit is the deepest and slowly it goes towards zero ...i.e. the particle becomes free.
    say for hydrogen atom the ionization energy is 13.6 ev .
    so the ground state n=1 is at -13.6 eV. so higher states will be closer to zero and the number will be smaller....
    so how one can see it .....
    say -13.6 eV is larger or smaller than -10 eV ?
    one has to supply +3.6 eV to the electron to raise it to -10 eV.
    and if an emission has taken place by transfer of electron from say E2 to E1 then E2 - E1 =h.frequency

    An electron in the lowest energy level of hydrogen (n = 1) therefore has about 13.6 eV less energy than a motionless electron infinitely far from the nucleus. The next energy level (n = 2) is −3.4 eV. The third (n = 3) is −1.51 eV, and so on. For larger values of n, these are also the binding energies of a highly excited atom with one electron in a large circular orbit around the rest of the atom.
    see wikipedia <https://en.wikipedia.org/wiki/Bohr_model#Origin> for detail discussion
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