JEE Main 2022 · 27 Jun · Shift 1 · Physics Q54

← JEE Main 2022 · 27 Jun · Shift 1

PhysicsInteger+4 / -1Question 54 of 90

A beam of monochromatic light is used to excite the electron in $\mathrm{Li^{++}}$ from the first orbit to the third orbit. The wavelength of monochromatic light is found to be $x\times10^{-10}$ m. The value of $x$ is ______.

[Given $hc=1242$ eV nm]

Your answer

Answer and worked solution

Official answer: 114

Energy for $\mathrm{Li^{2+}}$ ( $Z=3$ ), 1 → 3: $13.6\times9\left(1-\frac19\right)=108.8$ eV.

Wavelength. $\frac{1242}{108.8}\approx11.4$ nm $=114\times10^{-10}$ m.

Answer: 114

Topics:Bohr model and hydrogen spectrum

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JEE Main 2022 · 27 Jun · Shift 1, Physics question 54