### When do we use the Einstein Equation?

Posted:

**Sun Oct 20, 2019 4:59 pm**Hello :) I'm kinda confused about when exactly we use the Einstein Equation. Also, is it something that's used a lot? Thank you!

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=15&t=48237

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Posted: **Sun Oct 20, 2019 4:59 pm**

Hello :) I'm kinda confused about when exactly we use the Einstein Equation. Also, is it something that's used a lot? Thank you!

Posted: **Sun Oct 20, 2019 5:14 pm**

I'm pretty sure we use E=hv to find the energy of a photon

Posted: **Sun Oct 20, 2019 5:29 pm**

Im pretty sure it's used a lot because you can also isolate frequency in λv=C and subsitute it back into E=hv to find wavelength.

Posted: **Sun Oct 20, 2019 5:39 pm**

Like Taryn said, we use it to find energy/photon, substitute it in the rydberg equation (the equation used to find frequency, energy,et.c. of light when electrons go up/down quantum levels) & c=v(wavelength. it's used a lot; besides c=v(wavelength) I think it's probably one of the most commonly used (especially since we're talking about photons/electrons a lot) :)

Posted: **Sun Oct 20, 2019 9:52 pm**

The Einstein equation is used to solve for energy of an electron, but can also be useful to solve for other things such as frequency because that equation is C=(lambda)v.

Posted: **Sun Oct 20, 2019 10:15 pm**

It is used to solve for the energy of the photon. You also use it with the C=λν equation a lot.

Posted: **Sun Oct 20, 2019 11:06 pm**

E = hv is used to solve for the energy of an electron.

Sometimes you are not given v (frequency) therefore you must use c = λν, substituting the v in E=hv for v = c/ λ:

so E = hc/ λ

Sometimes you are not given v (frequency) therefore you must use c = λν, substituting the v in E=hv for v = c/ λ:

so E = hc/ λ

Posted: **Sun Oct 20, 2019 11:25 pm**

We would use the equation in order to find the energy of a photon. However, it does have other uses.

Posted: **Sun Oct 20, 2019 11:32 pm**

How often would you have to rearrange this equation to find other quantities? Should this be practiced?

Posted: **Sun Oct 20, 2019 11:42 pm**

E = hv is used in general to find the energy of a photon, although it can also be interpreted to find the energy required to remove an electron. On the topic of quantum, E = hv is most likely going to be a major equation.

Posted: **Sun Oct 20, 2019 11:43 pm**

Sean1F wrote:How often would you have to rearrange this equation to find other quantities? Should this be practiced?

The rearrangment of this equation would be most likely to find the energy required to remove an electron, or finding the wavelength of a photon/electron. It should be practiced as I believe finding these two quantities will also be common on the topic of quantum.

Posted: **Fri Oct 25, 2019 11:36 pm**

The equation E=hv can also easily be rearranged to be used to solve for v as well if you know Energy. Planck's constant will always be the same.

Posted: **Tue Nov 12, 2019 9:00 pm**

When relating energy of a photon to frequency, we use Einsteins equation. And if kinetic energy=0, we can also use it for the energy required to remove an electron. So, E = hv is used for relating the energy of a photon to its frequency, (remember that energy of a photon and its frequency are directly proportional)

Posted: **Tue Dec 03, 2019 8:10 pm**

You would use it to calculate the energy of an electron

Posted: **Wed Dec 04, 2019 6:14 pm**

E=hv will give you the energy of a photon. You should use it when finding frequency given energy or to find energy when given frequency.