JEE Main 2017 · 8 Apr · Shift 1 · Chemistry Q36

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ChemistrySingle correct+4 / -1Question 36 of 90

If the shortest wavelength in Lyman series of hydrogen atom is A, then the longest wavelength in Paschen series of $\ce{He+}$ is :

\dfrac{5A}9

\dfrac{9A}5

\dfrac{36A}5

\dfrac{36A}7

Answer and worked solution

Official answer: D

The shortest Lyman line of H is $\dfrac1A=R$ . The longest Paschen line of $\ce{He+}$ ( $Z=2$ , 4 → 3):
$\frac1\lambda=4R\left(\frac19-\frac1{16}\right)=\frac{7R}{36}\implies\lambda=\frac{36A}7.$

Topics:Bohr model Photoelectric effect and spectra

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JEE Main 2017 · 8 Apr · Shift 1, Chemistry question 36