## Changing negative to positive for change in energy

H-Atom ($E_{n}=-\frac{hR}{n^{2}}$)

Jordan_Wesson_2J
Posts: 59
Joined: Fri Sep 28, 2018 12:26 am

### Changing negative to positive for change in energy

In lecture today, Dr. Lavelle said the reason you change the sign for the change in energy to a positive when you plug it into the E=hv and I forgot what he said. Can someone please help explain?

Danielle_Gallandt3I
Posts: 70
Joined: Fri Sep 28, 2018 12:24 am

### Re: Changing negative to positive for change in energy

When you are plugging in the E value for the equation E=hv the energy input is the energy of a photon. When you use the equation E= -hR/n^2 you are calculating the energy an electron lost when going down one or more energy levels. The energy the electron lost is emitted as a photon. Since the electron is emitting/losing energy, its E value is negative. However, the energy the electron lost equals the energy of the photon, which is a positive value. This means when you plug in the E in the equation E=hv you are plugging in the positive energy value of the photon that was emitted.