## Energy Equations

$E=hv$

klarratt2
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

### Energy Equations

When do you use E=hv and when do you use E=pc? Are they interchangeable?

Iris Bai 2K
Posts: 60
Joined: Fri Sep 28, 2018 12:18 am

### Re: Energy Equations

You use E=hv when looking at light as a wave, and you use E=pc when looking at light as a particle.

Manya Bali 4E
Posts: 66
Joined: Fri Sep 28, 2018 12:23 am

### Re: Energy Equations

These equations should both find the energy for a photon (J). However, they use different variables to find E such as p (momentum), c (speed of light), h (Planck's constant), and v (wavelength). Depending on what you're given, you can use either one.

This is a bit more than you asked, but you can also manipulate E = hv and c = (wavelength)v to get E = hc/(wavelength). From there you can put the two equations together, get rid of c, and "derive" De Broglie's Wave Equation (wavelength) = h/p.

Imelda Mena 3I
Posts: 51
Joined: Thu Oct 02, 2014 3:00 am

### Re: Energy Equations

Hi, so just to clarify the v in the equation E=hv is not velocity but frequency?

Hannah Morales 1D
Posts: 31
Joined: Fri Sep 29, 2017 7:06 am

### Re: Energy Equations

Yes the v in this equation is frequency