[polkadotti101]

What is the energy change when the electron in a hydrogen atom undergoes a transition from the 4th energy level to the 2nd energy level? What is the wavelength of the photon emitted?

I've already worked out the first part of the question, which is E=4.09*10^-19J

Just wondering how to find the wavelength.

λphoton = hc / Ephoton

λphoton= (6.626*10^-34Js)(2.998*10^8ms^-1) / (4.09*10^-19J)
λphoton= 4.8569*10^-45

That's the answer I get but the answer is meant to be 486*10^-9m = 486nm
Where I am going wrong?

[mikasaur]

You must be entering a value in your calculator wrong. Double check you're not fat fingering anything.

[Borek]

You divided by 4.09×10¹⁹ instead of 4.09×10^-19.