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JEE Main 2020 (9 Jan, Shift 2) · Transitions, Photon Emission & Excitation

Transitions, Photon Emission & Excitation question from JEE Main 2020 (9 Jan, Shift 2)

Q51JEE Main 2020 · 9 JAN · SHIFT 2Medium

Transitions, Photon Emission & Excitation

The energy required to ionise a hydrogen like ion in its ground state is 9 Rydbergs. What is the wavelength of the radiation emitted when the electron in this ion jumps from the second excited state to the ground state?

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Answer: (b)

  1. Ionisation energy =Z2×1= Z^2 \times 1 Ry =9= 9 Ry ⇒Z=3\Rightarrow Z = 3.
  2. Second excited state is n=3n = 3: E=9×13.6×(1−19)=108.8E = 9 \times 13.6 \times \left(1 - \frac{1}{9}\right) = 108.8 eV
  3. λ=1240108.8\lambda = \frac{1240}{108.8} nm =11.4= 11.4 nm
  4. So the answer is (b) 11.4 nm.
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