Is a photon's momentum transverse?

In summary, the momentum carried by a photon is always in the direction of its motion and does not have a transverse component. This is separate from the classical electromagnetic wave picture, where transverse motion is observed.
  • #1
ConradDJ
Gold Member
319
1
I understand that light propagates as a transverse wave -- does this mean that the momentum carried by a photon is perpendicular to its path?

Thanks for the help.
 
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  • #2
No. The momentum of a photon (and of an electromagnetic wave) is in the direction of motion.

(Don't think of the photon as wiggling transversely as it travels; keep the classical electromagnetic wave picture and the photon picture separate.)
 
  • #3
As Doc Al states, the momentum of a photon is only in the direction of motion. If the photon strikes an electron and produces a photo electron (photoelectric effect). The transverse momentum of the electron (relative to the incoming photon direction) has to be balanced by the transverse momentum of the recoiling atom or lattice.
 

1. What is the definition of a photon's momentum?

A photon's momentum is the product of its mass and velocity. Since photons are massless particles, their momentum is solely determined by their velocity.

2. How is a photon's momentum different from its energy?

A photon's momentum is directly related to its energy through the equation E = pc, where p is momentum and c is the speed of light. However, momentum refers to the particle's motion and direction, while energy refers to its ability to do work.

3. Is a photon's momentum always transverse?

Yes, by definition, a photon's momentum is always transverse. This means that its direction of motion is perpendicular to the direction of its wave oscillation. This is a unique property of photons as they are the only particle that can have a transverse momentum.

4. How is the transverse momentum of a photon measured?

The transverse momentum of a photon can be measured indirectly through its effects on other charged particles, such as in the Compton scattering experiment. It can also be measured directly using sophisticated instruments like particle detectors.

5. Why is the transverse momentum of a photon important in physics?

The transverse momentum of a photon is important in understanding the behavior of light and electromagnetic radiation. It also plays a crucial role in the theories of quantum mechanics and relativity, where the concept of transverse momentum is used to explain the behavior of subatomic particles and the structure of space-time. Additionally, transverse momentum is used in practical applications such as in medical imaging and telecommunications.

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