Discussion Forum



1)

If the series limit frequency of the Lyman series is vL, the the series limit frequency of the Pfund series is 


A) $25v_{L}$

B) $16v_{L}$

C) $\frac{v_{L}}{16}$

D) $\frac{v_{L}}{25}$

Answer:

Option D

Explanation:

Key idea Series limit occurs in the transition n2= $\infty$  to n1= 1 in Lyman series and n2= $\infty$  to n1 =5 in pfund series. For Lyman series,

482019200_lyman.JPG

 $hv_{L}=13.6$      ..........(i)

  In pfund series

 482019622_lymann.JPG

$hv_{p}=\frac{13.6}{5^{2}}$ ........(ii)

 From Eqs. (i) and (ii), we get

 $25hv_{p}=hv_{L}$

$\therefore$ $v_{p}=\frac{v_{L}}{25}$