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Mass of Light

Posted: Mon Oct 15, 2018 8:16 pm
How is the mass of light calculated? I know it can only have a mass when it is in motion and not when it's stationary.

Re: Mass of Light

Posted: Mon Oct 15, 2018 9:05 pm
I thought it only has energy and momentum, and negligible mass? Can someone clarify?

Re: Mass of Light

Posted: Tue Oct 16, 2018 12:08 pm
I don't think you can calculate the mass of light. We are given the speed of light which is the constant c=2.99792x10^8 ms^-1, but the mass of light is I believe negligible as someone has already said.

Re: Mass of Light

Posted: Tue Oct 16, 2018 1:14 pm
Like they said above, light doesn't have mass. A photon acts like a particle rather than a wave, but that "particle" is only used for visualizing discrete amounts of energy, 1:1 photon:electron interactions, etc. A photon has a velocity as well.

Re: Mass of Light

Posted: Tue Oct 16, 2018 1:21 pm
Additionally, light does not exist when it is not moving. Unlike an object like an electron, which is said to have a “rest mass”, light has no mass when it is not moving because it doesn’t exist when it is resting. Something must be in existence when it is not moving for its mass to be measured. Objects with rest mass can therefore not have a velocity faster than the speed of light because light has no mass.

Re: Mass of Light

Posted: Tue Oct 16, 2018 5:37 pm
Light does not have a rest mass, so you can't calculate the mass of light.