### energy equation

Posted:

**Wed Oct 17, 2018 4:53 pm**How do I know when to use just the equation E=hv or when to use E=(hc)/v to find the energy of a photon?

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=14&t=34041

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Posted: **Wed Oct 17, 2018 4:53 pm**

How do I know when to use just the equation E=hv or when to use E=(hc)/v to find the energy of a photon?

Posted: **Wed Oct 17, 2018 4:58 pm**

did you mean E = hc/λ?

Posted: **Wed Oct 17, 2018 5:14 pm**

You will know depending on the variables given. If the variables don't quite line up with the energy equation, most likely you will have to use the other one and see if that works. Also make sure you distinguish the variable the problem is asking for.

Posted: **Wed Oct 17, 2018 5:19 pm**

I think it depends on what the question already gives you data-wise. If one of the equations isn't possible to use because a specific data point isn't given, then switch to the other and see from there.

Posted: **Fri Oct 19, 2018 3:54 pm**

The above poster is correct.

The equation you are looking for is E = hc/λ

λ = wave length

E = energy

h = Planck constant

c = speed of light

H and C will be provided in the information sheet in the test.

The equation you are looking for is E = hc/λ

λ = wave length

E = energy

h = Planck constant

c = speed of light

H and C will be provided in the information sheet in the test.