JEE Mains · Physics · STD 12 - Atoms
- JEE Mains 2024
- Hard
- MCQ
The longest wavelength associated with Paschen series is _______. (Given \(R_H=1.097 \times 10^7 \mathrm{SI}\) unit)
Pick an option to check your answer.
Answer & Solution
Correct Answer
(D) \(1.876 \times 10^{-6} \mathrm{~m}\)
Step-by-step Solution
Detailed explanation
For longest wavelength in Paschen's series:
\(\frac{1}{\lambda}=\mathrm{R}\left[\frac{1}{\mathrm{n}_1{ }^2}-\frac{1}{\mathrm{n}_2{ }^2}\right]\)
\(\text { For longest } \mathrm{n}_1=3\)
\(\frac{1}{\lambda}=\mathrm{n}\left[\frac{1}{(3)^2}-\frac{1}{(4)^2}\right]\)
\(\frac{1}{\lambda}=\mathrm{R}\left[\frac{1}{9}-\frac{1}{16}\right]\)
\(\frac{1}{\lambda}=\mathrm{R}\left[\frac{16-9}{16 \times 9}\right]\)
\(\Rightarrow \lambda=\frac{16 \times 9}{7 \mathrm{R}}=\frac{16 \times 9}{7 \times 1.097 \times 10^7}\)
\(\lambda=1.876 \times 10^{-6} \mathrm{~m}\)
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