99 Percentile Qs Bank for JEE MainPhysicsAtomic Physics
Let _P and _L be the longest wavelengths observed in the Paschen and Lyman series respectively. Choose the correct option
Options
- A4 < _ _L < 6
- B7 < _ _L < 8
- C15 < _ _L < 16
- D30 < _ _L < 32
Correct answer
C. 15 < _ _L < 16
Step-by-step solution
As we know, wavelength for Paschen-series. 1 _P =R [ 1 3^2 - 1 n_p^2 ], n_p=4,5,6 and wavelength for Lyman-series, 1 _L =R [1- 1 n_L^2 ], n_L=2,3,4 Hence, _p for n_p=4 1 _p =R [ 1 9 - 1 16 ],= 7 R 9 16 and _L for n_L=2 1 _L =R [1- 1 4 ]= 3 R 4 From Eq. (i) and (ii), we get _p _L = 3 R / 4 7 R / 9 16 =15.42 So, 15 < _P _L < 16 Hence, the correct option is (c).