If a photon of light has mass, what is it's mass? Is it same for all types of light (Infrared, visible, UV)?

Question

I've always marvelled at the whole concept of light as a particle and simultaneously as a wave. I understand the basics of E=MC2, but wondering if light is a particle, how much mass does it have? Is the mass dependent on how excited the photon is? I guess I'm kind of answering my own question a bit. Well, maybe not...

Ok but how is something that has no mass considered a "particle"?

Answer 1

Light only acts as a particle in that in can transfer energy. Light isn't "made up of photons" so to speak. It's not that when you turn on a light it shoots little balls out that then cause light. What's really happening is energy is being transferred across the electromagnetic spectrum.

So when you turn on a lightbulb, the little electrons in the filament are energized, and they begin to wave. They vibrate back and forth extremely fast. This causes a light wave to be sent out. When the light wave contacts something else, it transfers "1 photon of energy" to whatever particle it crosses. So when light is traveling, it does so as a wave. But when it interacts with matter, it actually transfers energy the same way as if it were another particle. When the light wave hits that particle and transfers its photon of energy, it will cause the electrons on that new particle to begin waving.

If you'd like to learn more, there are lots of texts about quantum mechanics that deal with interactions between light and matter.

Answer 2

Wave properties are inherent in every photon. But when in a stream of photons wave properties cannot be explained .

Thus a photon can in no way be viewed as an ‘ordinary’ particle.


In creating a model of the INVISIBLE world, we endow elementary particles with properties BORROWED from the world of things ( materials) around us, or, as they say in physics, from the macro world.

Thus, for example, atoms are conceived as spherules.

However, an atom spherule, does not reflect all the properties of the material spherule.

The color, roughness and odour cannot be transferred to a spherule.

The more we penetrate into the micro world, the more difficult it is to endow elementary particle with material particle.

Photon resembles a material spherule even less than an atom spherule does.

In a macro world a particle is particle and a wave is a wave.

A particle occupies a limited region of space and travels along a definite path.

A wave is distributed continuously in space and the energy is transmitted to one or another region from all points in space.

For materials these two views are incompatible.

But we have no right to impose the behavior of materials on particles of micro world.

Cognition of the micro world does not consist in the creation of a model resembling the pictures familiar to the human eye.

The infinite process of cognition consists in the investigation of the regularities of phenomena, the determination of objectively existing casual relationships between phenomena.

In this manner, a complex picture of micro world, whose essence cannot be transmitted by any ingenious model borrowed from the macro world, is obtained.


The answer to your question in light of the above explanations is
They are massless particles at rest however with energy and momentum they have relativistic mass which changes with velocity or increases with their speed which is simply a quantity that does not depend on the observer or the inertial frame used to observe it

Answer 3

The photon has no rest mass. It does have an energy E=hf where f is the frequency.

Answer 4

Photons have zero mass. However, they do have momentum, and they exert pressure when they collide with an object.

Answer 5

i think it's zero