Hydrogen spectrum problem

Question

A wavelength of 4.653 um is observed in a hydrogen spectrum for a transition that ends in the nf= 5 level. What was ni for the initial level of the electron?

Answer 1

λ = 4.653E-6m

nf = 5

R = 1.09E-7 m^-1...........Rydberg constant

ni = ?

equation

1/λ = R(1/nf² - 1/ni²)

rearrange & substitute

ni = √[1/(1/nf² - 1/λR)] = 7

,.,.,