Do photons have mass?

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Multiple Choice

Do photons have mass?

Photons are massless particles that carry energy and momentum. In relativity, a particle’s rest mass is the amount of inertia it has when it’s at rest, but photons always travel at the speed of light, so their rest mass is zero. Despite lacking rest mass, they have energy E = hν and momentum p = E/c, which is why they can interact with matter and transfer momentum, producing effects like radiation pressure. So describing photons as weightless bundles of energy with no mass captures the essential idea: they have energy and momentum without possessing rest mass. They don’t acquire mass during interactions, and they don’t have negative mass.

Photons are massless particles that carry energy and momentum. In relativity, a particle’s rest mass is the amount of inertia it has when it’s at rest, but photons always travel at the speed of light, so their rest mass is zero. Despite lacking rest mass, they have energy E = hν and momentum p = E/c, which is why they can interact with matter and transfer momentum, producing effects like radiation pressure. So describing photons as weightless bundles of energy with no mass captures the essential idea: they have energy and momentum without possessing rest mass. They don’t acquire mass during interactions, and they don’t have negative mass.

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