What is the difference between deltaE=hv and E=hv?

[Nhi Vo 3A]

#10 in workbook: An excited hydrogen atom emits light with a frequency of 1.14 x 10^14 Hz to reach the energy level for which n=4. In what principle quantum level did the electron begin?

The worked out solution uses the equation deltaE= hv to find energy. My confusion is how do I know when the equation, E=hv, is just E or delta E ?

Thank you

[Tiffany_Hoang_3C]

ΔE is the change in energy (which can be positive or negative and can be found if given the frequency/wavelength of a light emitted/absorbed when an electron moves to a different energy level) while E is simply the energy of a given wavelength/frequency. In #10, we subtract the E of the energy level we are trying to find from the E when n=4 (since the electron is going to a lower energy state). We then find the energy state that the electron goes to by setting the difference equal to ΔE.

[Yolandia Winn 1A]

good explanation^^ From my understanding, you use deltaE=hv when there is a change, a loss or a gaining of Energy.
E=hv is an equation that tells you how much energy a photon has in this moment.

[William Cryer 1L]

We want to know where the hydrogen atom started (that is, which principle quantum level it was in). We need to know how much energy it gained or lost in order to get into the energy level, n=4. We would use deltaE=hv, as we need to know how much energy was used or lost in this process (the delta symbol mean change in Greek).

[mayasinha1B]

Delta E is the change in energy, E(final)-E(initial), while just E would be the calculation of energy at a given energy state, n.

[Sam Smoot 2L]

∆E is the change in energy (final energy - initial energy). It seems that sometimes it will simply be written as E when in context it actually means ∆E.