ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: Adapt on July 13, 2019, 01:06:10 pm
-
Hey guys, I was just wondering, I was given a certain frequency of light, and I was asked to calculate the momentum of the photon. Do I use plancks constant in joules or eV? How do you know when to use eV or J in other cases?
-
Hey guys, I was just wondering, I was given a certain frequency of light, and I was asked to calculate the momentum of the photon. Do I use plancks constant in joules or eV? How do you know when to use eV or J in other cases?
I would actually suggest using de Broglie wavelength equation to find the momentum of a photon. Planck's equation is usually used to find the energy of a photon. (In the end it is really ur choice though ).
Anyway to answer your question:
The energy of a photon is in joules. If you are going to use planck's equation it would possibly be in joules. Hope that answered ur question.
P.S. In case u were wondering what is de brogile wavelength equation :
p = h / lambda
where h is planck's constant and lambda is wavelength of the certain frequency of light ( u can find wavelength of light through frequency as speed of light = wavelength * frequency
-
I would actually suggest using de Broglie wavelength equation to find the momentum of a photon. Planck's equation is usually used to find the energy of a photon. (In the end it is really ur choice though ).
Anyway to answer your question:
The energy of a photon is in joules. If you are going to use planck's equation it would possibly be in joules. Hope that answered ur question.
P.S. In case u were wondering what is de brogile wavelength equation :
p = h / lambda
where h is planck's constant and lambda is wavelength of the certain frequency of light ( u can find wavelength of light through frequency as speed of light = wavelength * frequency
Sorry maybe I worded it incorrectly, I am using de Broglie’s equation, but with the h in that equation, do you sub in h in J or eV?
-
Sorry maybe I worded it incorrectly, I am using de Broglie’s equation, but with the h in that equation, do you sub in h in J or eV?
Planck's constant is measured in joule seconds. The unit for the momentum of a photon is actually kilogram metres per second. This is because de broglie wavelength is measured in meters and (as I said before) planck's constant is measured in joule seconds.
If this sounds confusing, please refer to an example of find the momentum of a photon I found on the internet for you :)
http://www.softschools.com/formulas/physics/photon_momentum_formula/542/