posted by lorah hilpolep .
An electron in a hydrogen atom relaxes to the n= 4 level, emitting light of 138 THz.
What is the value of n for the level in which the electron originated?
a. figure energy for the photon, for the given frequency. E=hf
b. then, E= constant(1/n^2-1/16)
I can check your work if necessary.