Question

Hydrogen exhibits several series of line spectra in different spectral regions. For example the Lyman series ( nf = 1 in Balmer-Rydberg equation) occurs in the ultraviolet region while the Balmer ( nf = 2) series occurs in the visible range and the Paschen ( nf = 3), Brackett ( nf = 4) and Pfund ( nf = 5) series all occur in the infrared range. What is the wavelength (in nm) of a line in the Pfund series where ni = 10?

Answer 1

ν˜=1/λ=R_H(1/n²₁−1/n²₂)

Where R_H is the Rydberg constant and is equal to 109,737 cm^-1.

Pfund series n₁=5

n₂=10

1/λ=109,737(5^-2-10^-2) cm^-1

      =109,737(0.03)

      =3292.11cm^-1

λ = 3.0375655×10^-4×10⁷nm

  =3037.57nm