If the series limit frequency of the Lyman series is $\nu_{L}$, then the series limit frequency of the Pfund series is:

JEE Main · 2018 · 08 Apr 2018 · Offline · Modern Physics

If the series limit frequency of the Lyman series is

ν_{L}

, then the series limit frequency of the Pfund series is:

(A) $ν_{L} /25$ ✓ Correct
(B) $25 ν_{L}$
(C) $16 ν_{L}$
(D) $ν_{L} /16$

Answer: (A)

Solution

A series limit is the transition from

n = \infty

down to the series' lowest level, so its frequency is

R c Z^{2} \frac{1}{n _{f}^{2}}

. The Lyman limit ends at

n_{f} = 1

, giving

ν_{L} = R c Z^{2}

, while the Pfund limit ends at

n_{f} = 5

, giving

ν_{P} = \frac{R c Z ^{2}}{25}

, so that

ν_{P} = \frac{ν _{L}}{25}

JEE Main · 2018 · 08 Apr 2018 · Offline · Single correct option

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