JEE Main 2019 — Physics solution

JEE Main2019Physics

In Li⁺⁺, electron in first Bohr orbit is excited to a level by a radiation of wavelength $λ$ . 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 $λ$ ?

(Given: h = 6.63 × 10^–34 Js; c = 3 × 10⁸ ms^–1)

A
11.4 nm
B
12.3 nm
C
9.4 nm
D
10.8 nm

Solution

$Δ E = \frac{h c}{λ} = (13.4) (3)^{2} [1 - \frac{1}{16}] e V \Rightarrow λ = \frac{1242 \times 16}{( 13.4 ) \times ( 9 ) ( 15 )} nm ≃ 10.8 nm$

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