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Structure of Atom question

2022 · 26 Jul · Shift 1 · Q17
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Structure of Atom question

2022 · 26 Jul · Shift 1 · Q17

JEE MainChemistryStructure of AtomNumerical+4 / −1
The wavelength of an electron and a neutron will become equal when the velocity of the electron is xxx times the velocity of neutron. The value of xxx is ‾\underline{\hspace{2cm}}​. (Nearest Integer) (Mass of electron is 9.1×10−31 kg9.1 \times 10^{-31} \mathrm{~kg}9.1×10−31 kg and mass of neutron is 1.6×10−27 kg1.6 \times 10^{-27} \mathrm{~kg}1.6×10−27 kg )
Numerical answer
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Correct answer: 1758

  1. For a particle, the de Broglie wavelength is λ=hmv\lambda = \frac{h}{mv}λ=mvh​ where hhh is Planck’s constant, mmm is mass, and vvv is velocity.

  2. Let the electron have mass mem_eme​ and velocity vev_eve​, and the neutron have mass mnm_nmn​ and velocity vnv_nvn​.

    Their wavelengths are equal, so hmeve=hmnvn\frac{h}{m_e v_e} = \frac{h}{m_n v_n}me​ve​h​=mn​vn​h​ Cancelling hhh: meve=mnvnm_e v_e = m_n v_nme​ve​=mn​vn​

  3. We are told that the velocity of the electron is xxx times the velocity of neutron: ve=xvnv_e = x v_nve​=xvn​ Substitute into the wavelength condition: me(xvn)=mnvnm_e (x v_n) = m_n v_nme​(xvn​)=mn​vn​ Cancelling vnv_nvn​: mex=mnm_e x = m_nme​x=mn​ So, x=mnmex = \frac{m_n}{m_e}x=me​mn​​

  4. Substitute the given masses: x=1.6×10−279.1×10−31x = \frac{1.6 \times 10^{-27}}{9.1 \times 10^{-31}}x=9.1×10−311.6×10−27​ x=1.69.1×104x = \frac{1.6}{9.1} \times 10^{4}x=9.11.6​×104 x≈0.17582×104x \approx 0.17582 \times 10^{4}x≈0.17582×104 x≈1758.24x \approx 1758.24x≈1758.24

  5. Nearest integer: x=1758x = 1758x=1758

Therefore, the required value is 1758.

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