JEE MAIN - Physics (2019 - 10th April Evening Slot - No. 8)

In Li^{+ +}, electron in first Bohr orbit is excited to a level by a radiation of wavelength $$\lambda $$. When the ion gets deexcited to the ground state in all possible ways (including intermediate emissions), a total of six spectral lines are observed. What is the value of $$\lambda $$?
(Given : H = 6.63 × 10^–34 Js; c = 3 × 10⁸ ms ^–1)

10.8 nm

12.3 nm

9.4 nm

11.4 nm

Explanation

$${{hc} \over \lambda } = 13.6\,ev(g)\left\{ {1 - {1 \over {16}}} \right\}$$

$${{1240\,eV} \over \lambda } = {{15} \over {16}} \times 9 \times 13.6\,eV$$

$$\lambda = {{1240 \times 16} \over {15 \times 9 \times 13.6}} = 10.8\,nm$$

JEE MAIN - Physics (2019 - 10th April Evening Slot - No. 8)

Explanation

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