What energy is required to excite a hydrogen atom in its n = 2 state to the n = 3 state ?

Answer 1

Isn't this the point of the Rydberg equation?

1/lambda= R(1/n^2 -1/m^2)

but E=plancksConstant*c/lambda

so E=plancksconstant*c * R (1/n^2-1/m^2)

c is the speed of light, R is the Rydberg constant, m,m are the two states.

What is neat about this method is it can be 'extended' to other atoms, by the multiplication Z^2 where Z is the atomic number.