[schrodingersdog]

I recently did a problem on this, and used E=nhv but it gave off a wrong answer. When I checked the answer, they used E=hv. However, the question gave me n, so why can't I use the first formula?
Btw, this is the question:
An excited hydrogen atom emits light with a wavelength of 397.2 nm to reach the energy level for which n = 2. In which principal quantum level did the electron begin?

Thanks for taking the time to read this, my Midterm starts on Monday so I would appreciate it if someone could help me out asap 

[Corribus]

Have you learned the Rydberg formula?

[schrodingersdog]

Yes

[Corribus]

Well then that is the formula you should be using along with the n value given,  to determine the unknown n value.

[Enthalpy]

n is a number of photons in nhν. Elsewhere, it is an energy level.

[schrodingersdog]

Oh ok I got it! Thanks