Find the energy (in joules) of the photon that is emitted when the electron in a hydrogen atom undergoes a transition from the n=7 energy level to produce a line in the Paschen series.

Answer 1

Paschen series are to n=3

n=7 so n^2 = 49
n=3 so n^2 = 9

use the Rydberg formula

1/lambda = Rh(1/9 - 1/49)

where Rh = 1.097 x 10^7 m^-1

then convert the wavelength (lambda) to energy using E=hf