Can Photons Really Have Zero Momentum and Energy?

  • Context: Undergrad 
  • Thread starter Thread starter suchal
  • Start date Start date
  • Tags Tags
    Momentum Photons
Click For Summary
SUMMARY

Photons, the particles of light, possess zero rest mass, leading to the conclusion that their momentum (p) and energy (E) cannot be defined in the same way as massive particles. The equation E^2 = p^2 c^2 + m^2 c^4 illustrates that for photons, where the rest mass (m) is zero, the energy is directly related to momentum. Therefore, while photons travel at the speed of light, their relativistic mass does not apply, confirming that they have no rest energy or momentum in the traditional sense.

PREREQUISITES
  • Understanding of relativistic physics concepts
  • Familiarity with the equation E=mc²
  • Knowledge of momentum in physics (p=mv)
  • Basic grasp of the relationship between energy and mass
NEXT STEPS
  • Research the implications of massless particles in quantum mechanics
  • Study the derivation and applications of the equation E^2 = p^2 c^2 + m^2 c^4
  • Explore the concept of relativistic mass versus invariant mass
  • Investigate the role of photons in electromagnetic theory
USEFUL FOR

Students and professionals in physics, particularly those focusing on quantum mechanics and relativity, as well as educators seeking to clarify the properties of light and its behavior in various contexts.

suchal
Messages
32
Reaction score
1
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.
 
Physics news on Phys.org
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.
 

Similar threads

Undergrad How is photon momentum compatible with special relativity?
  • · Replies 19 ·
Replies
19
Views
3K
Graduate Orbits of a photon that can't quite cross the photon sphere of a BH
  • · Replies 1 ·
Replies
1
Views
597
Undergrad The Energy - Momentum Equation vs the Energy - Mass Equation
  • · Replies 131 ·
5
Replies
131
Views
12K
Undergrad Photon in a mirrored box moving in direction of travel
  • · Replies 26 ·
Replies
26
Views
2K
Undergrad Still have questions about photon mass
  • · Replies 22 ·
Replies
22
Views
2K
Graduate Dirac's "GTR" Eq (27.4): how momentum ##p^\mu## varies
  • · Replies 50 ·
2
Replies
50
Views
4K
Undergrad Meaning of the invariants built from the angular momentum tensor
  • · Replies 1 ·
Replies
1
Views
1K
Undergrad Understanding the Relationship Between Energy and Momentum in Special Relativity
  • · Replies 11 ·
Replies
11
Views
3K
Undergrad Does p=mc Apply To Photons? | A.P. French's Special Relativity
  • · Replies 15 ·
Replies
15
Views
2K
Undergrad Geodesics in Schwarzschild metric
  • · Replies 42 ·
2
Replies
42
Views
5K