JEE Mains · Physics · STD 12 - 12. atoms
A beam of monochromatic light is used to excite the electron in \(Li ^{++}\)from the first orbit to the third orbit. The wavelength of monochromatic light is found to be \(x \times 10^{-10} \; m\). The value of \(x\) is \(\dots.\) [Given hc \(=1242 \; eV nm ]\)
- A \(113\)
- B \(114\)
- C \(115\)
- D \(116\)
Answer & Solution
Correct Answer
(B) \(114\)
Step-by-step Solution
Detailed explanation
\(Z =3\) \(\frac{1}{\lambda}=R Z^{2}\left(\frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}}\right)\) \(n_{1}=1, \quad n_{2}=3,\) \(\frac{1}{\lambda}=R(9)\left(\frac{1}{1}-\frac{1}{9}\right)=8 \; R\) \(\lambda=\frac{1}{8 R}=114 \times 10^{-10} \; m\)
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