## HW Question 1A.15

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

Kelsey Ash 1D
Posts: 50
Joined: Wed Sep 18, 2019 12:16 am

### HW Question 1A.15

Whenever I solve this equation out am getting the the energy of the photon is 1.936x10^-18 J but there is apparently this whole answer is supposed to be negative. Could someone please explain why this is; where does the negative sign come from?

sarahforman_Dis2I
Posts: 109
Joined: Sat Aug 17, 2019 12:18 am

### Re: HW Question 1A.15

Kelsey Ash 1D wrote:Whenever I solve this equation out am getting the the energy of the photon is 1.936x10^-18 J but there is apparently this whole answer is supposed to be negative. Could someone please explain why this is; where does the negative sign come from?

Your math is correct. The positive value that you calculated is the energy of the photon, however the energy lost by the electron (which is the value you need) will be that whole number negative. I believe that the number is negative because we are thinking about how the electron has lost energy. The question states that this is an emission spectra, meaning that we are measuring the wavelengths of electromagnetic radiation released. Since EM radiation is released when electrons fall from a high energy level to a lower one, the value of energy the electron lost will be the negative of the energy released. Therefore the energy must have a negative value. I hope that this helps.