Physics
posted by Jenny .
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.

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