why photons have momentum?

suchal

p=mv then for a photon p=0*c means p=0. And also ke=1/2pv which is ke=0 and E=mc2 means E=0. please use easy words and we descriptive.

dextercioby

For <particles> of light, photons, certain care needs to be taken about what p,m,v,E mean. If p=mc, then m is the so-called 'relativistic mass' which has no meaning for a photon, but only for a massive particle.

The universal formula which is to be used is

[tex] E^2 = \vec{p}^2 c^2 + m^2 c^4 [/tex]

where m is the rest/invariant mass which is 0 for a photon.

lugita15

See the FAQ here. Also, you might find this thread interesting.

Similar Threads for: why photons have momentum?
Thread	Forum	Replies
Momentum: laser beam and photons	Introductory Physics Homework	2
relativistic momentum and photons	Special & General Relativity	4
Relativistic Zero Momentum Frame of Photons	Advanced Physics Homework	0
photons, mass, momentum	Special & General Relativity	1
energy, photons, angular momentum and polarization	Quantum Physics	7

suchal	why photons have momentum? Tweet p=mv then for a photon p=0*c means p=0. And also ke=1/2pv which is ke=0 and E=mc2 means E=0. please use easy words and we descriptive.

dextercioby Blog Entries: 9 Recognitions: Homework Help Science Advisor	For <particles> of light, photons, certain care needs to be taken about what p,m,v,E mean. If p=mc, then m is the so-called 'relativistic mass' which has no meaning for a photon, but only for a massive particle. The universal formula which is to be used is [tex] E^2 = \vec{p}^2 c^2 + m^2 c^4 [/tex] where m is the rest/invariant mass which is 0 for a photon.

lugita15 Blog Entries: 1	See the FAQ here. Also, you might find this thread interesting.