The wavelength of the radiation emitted,when a hydrogen atom electron falls from infinity to stationary state 1, would be (Rydberg constant =1.097×107 m-1)
91 nm
1λ=RnZ2(1n21-1n22)
1λ=1.097×107m−1(112-1∞)
Therefore, λ=91×10−9m
We know 10−9=1nm so λ=91nm