### Calculating energy

Posted:

**Sun Apr 22, 2018 12:40 am**Problem 1.25 on the homework gives wavelength asking to find energy emitted by a photon. How would you calculate that?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=17&t=30952

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Posted: **Sun Apr 22, 2018 12:40 am**

Problem 1.25 on the homework gives wavelength asking to find energy emitted by a photon. How would you calculate that?

Posted: **Sun Apr 22, 2018 10:47 am**

Since you are given the wavelength you can solve for the frequency since the c in this equation is a constant c=(wavelength)(frequency). Then the Energy equation is E=h*(frequency). Since you just found frequency and h is a constant then you can solve for the energy. Or you can simply just use the equation E=hc/(wavelength) if you want to do it in one step.

Posted: **Sun Apr 22, 2018 11:25 am**

I suggest using unit cancellation or dimensional analysis to solve questions like these. You have all the equations you need and the givens required to use simple cancellation and number crunching :)

Posted: **Sun Apr 22, 2018 12:08 pm**

Like everyone has said, just because there is not a given equation for energy in terms of what is given doesn't mean that you can't rearrange two equations to obtain what you want. Combine the equations E=h(frequency) and c=v (frequency)