How Do You Calculate the Wavelength of an Electron Transition in a Helium Ion?

[amit25]

Homework Statement

He+ ion consists of a nucleus which is an alpha particle plus one orbiting electron.Hence it has a net positive charge.
a)Derive an expression for the electron state energies
b)what is the wavelength associated with a transition between the lowest two energy states?

Homework Equations

The Attempt at a Solution

For part a) i figured it out to be E=(-4R)/(n^2) where R is the rydbergs constant
for part b) I am having trouble not sure where to begin

 

[Serac]

Don't forget, the wavelength of a photon emitted, for a drop in energy level, is proportional to the difference in energies between the two levels.

I think that will be useful.

 

[amit25]

should i use this

ΔE = RchZ²{1/n²(1) - 1/n²(2)}

where R is the Rydberg constant (1.0974 x 10E7 m-¹); c the speed of light in vacuum (2.9979 x 10E8 m s-¹); h Planck's constant (6.626 x 10E-34 J s); Z nuclear charge; n(1) & n(2) are the principal quantum numbers of the electron transition