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  • If wavelength of the first line of the Paschen series of hydrogen atom is ,then the wa

If wavelength of the first line of the Paschen series of hydrogen atom is 720 \mathrm{~nm},then the wavelength of the second line of this series is \mathrm{nm}. (Nearest integer)

Option: 1

492


Option: 2

-


Option: 3

-


Option: 4

-


Answers (1)

best_answer

Paschen series :-
\mathrm{z}=1

\mathrm{I}^{\text {st }}$ line $:-4 \rightarrow 3
\frac{1}{\lambda}=\mathrm{R} \times(1)^2\left(\frac{1}{3^2}-\frac{1}{4^2}\right)
\frac{1}{720}=\mathrm{R}\left(\frac{7}{144}\right)\quad \quad(1)

\mathrm{II}^{\text {nd }}$ line $\rightarrow 5 \rightarrow 3
\frac{1}{\lambda}=\mathrm{R} \times(1)\left(\frac{1}{3^2}-\frac{1}{5^2}\right)
\frac{1}{\lambda}=\mathrm{R}\left(\frac{16}{225}\right)\quad \quad(2)

Equation (2) \div equation (1)
\frac{\lambda}{720}=\frac{7}{144} \times \frac{225}{16}
\lambda=492.18

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Gunjita

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