## E=hv vs E=pc?

$E=hv$

Ami_Pant_4G
Posts: 90
Joined: Sat Aug 24, 2019 12:17 am

### E=hv vs E=pc?

What is the difference between E=hv and E=pc? The notes made it seem that thy were both used to calculate energy of the photon, so would that mean the only difference is the circumstance in which you would use them?

AGulati_4A
Posts: 74
Joined: Sat Sep 07, 2019 12:19 am

### Re: E=hv vs E=pc?

E= P*C is probably most likely not used in calculations. I think when it could be important is in the derivation of the De Broglie wave equation, which converts the P into mv and C into (lambda)(frequency) in order to find the De Broglie equation

TarynD_1I
Posts: 85
Joined: Sat Aug 24, 2019 12:17 am

### Re: E=hv vs E=pc?

E=hv is used to find the energy of a photon using Planck's constant and frequency of light.
E=pc is used to find the energy of a photon using the speed of light and the momentum of a photon. I'm pretty sure we only use E=pc when momentum of the photon is provided.

jvera4b
Posts: 60
Joined: Wed Sep 11, 2019 12:17 am

### Re: E=hv vs E=pc?

E=hv would be used if the frequency is given or you can find it by manipulating c=(lambda)v, E=pc would be used when the momentum cana be found such as when the velocity or momentum is given.