Question

Wave number of a spectral line is 30000cm^-1. The series to ehich ot belongs is

Answer 1

wave number is the reciprocal of wavelength.

so, 1/λ = 30000 cm^-1

for hydrogen atom, Rydberg's equation is given as, 1/λ = R[1/n1² - 1/n2²]

⇒30000 cm^-1 = 109737.3 cm^-1 [1/n1² - 1/n2²]

⇒30000/109737.3 = [1/n1² - 1/n2² ]

⇒1/3.657 = [1/n1² - 1/n2² ]

⇒1/3.657 ≈ 1/4 = [1/n1² - 1/n2² ]

it is possible only when, n1 = 2 And n2 = ∞. means, Balmer's series.

hence, it belongs to Balmer's series.

[ note : here, atomic number of the element is not given . so, I used hydrogen atom. well, you know range of Balmer's series is 400nm to 700 nm. precisely we can say above spectral line belongs to Balmer's series. ]