Is Planck's Law Inconsistent With Equations Of Momentum

[JulianM]

Given that E = m.c^2

and that E = h.f

 

why can't we form a relationship for particles of light?

[Shustaire]

Your not using the correct first equation. That equation is the invariant or rest mass of a particle.

 

Photons has no rest mass

 

You need the energy/momentum equation

 

https://en.m.wikipedia.org/wiki/Energy–momentum_relation

Edited January 1, 2018 by Shustaire

[Super Polymath]

Your not using the correct first equation. That equation is the invariant or rest mass of a particle.

 

Photons has no rest mass

 

You need the energy/momentum equation

 

https://en.m.wikipedia.org/wiki/Energy–momentum_relation

They do according to my theory. 

[JulianM]

Super Polymath - what is your theory?

[exchemist]

Given that E = m.c^2

and that E = h.f

 

why can't we form a relationship for particles of light?

Shustaire is quite right of course. The energy momentum equation is the more general form, of which the famous E=mc² is a simplified special case. The more general form is able to account for entities such as photons that have zero rest mass but which nonetheless have energy and momentum. In fact the connection between it and E=hf is made via de Broglie's relation:

 

For a photon, the energy momentum relation reduces to E=pc. But de Broglie's relation tells us p=h/λ, so since  c=fλ, we can rewrite that as p=hf/c.  So we have E= (hf/c).c, i.e. E=hf.

 

Bingo!  And a rather nice connection between the two great discoveries in early c.20th physics: relativity and quantum theory. :)

Edited January 1, 2018 by exchemist

[Super Polymath]

Super Polymath - what is your theory?

http://www.scienceforums.com/topic/30701-can-someone-model-this-mathematically

 

No equation yet. 

[Shustaire]

Then a hypothesis. A theory requires equations for testability and predictions.

[Vmedvil]

Ya the , p²c²  part is just a different algebra solve of this.