How come photons have a momentum even though they do not have a mass?

In short, even though photons have no mass, they still have momentum proportional to their energy, given by the formula p=E/c. Because photons have no mass, all of the momentum of a photon actually comes from its energy and frequency as described by the Planck-Einstein relation E=hf.

Why does a photon have no mass?

Why do photons have no mass? In short, the special theory of relativity predicts that photons do not have mass simply because they travel at the speed of light. This is also backed up by the theory of quantum electrodynamics, which predicts that photons cannot have mass as a result of U(1) -gauge symmetry.

Why are photons affected by gravity if they have no mass?

Photons are massless due to the gauge invariance of electromagnetism. They are affected by gravitational fields–that describe spacetime curvature–because the motion of any form of matter, in curved spacetime, is described by its energy-momentum tensor.

Can photons have mass?

Since photons (particles of light) have no mass, they must obey E = pc and therefore get all of their energy from their momentum.

Is photon completely massless?

Light is composed of photons, so we could ask if the photon has mass. The answer is then definitely “no”: the photon is a massless particle. According to theory it has energy and momentum but no mass, and this is confirmed by experiment to within strict limits.

Why doesn’t mass affect gravity?

“What are the factors that affect the acceleration due to gravity?” Mass does not affect the acceleration due to gravity in any measurable way. The two quantities are independent of one another. Light objects accelerate more slowly than heavy objects only when forces other than gravity are also at work.

Can photons be diffracted?

It is not possible for a single photon to produce a diffraction pattern. However, this is only because it would be impossible to extrapolate a pattern with only one data point. So as the single photon’s wave function passes through the slits it is diffracted and interferes with itself.

Can a photon gain mass?

A photon can gain neither mass nor |momentum|. The only way you can alter a photon is by absorbing it. A photon, if it is energetic enough, can interact with a “seed charge”, and produce two massive particles, such as an electron and a positron, plus some waste energy.