Relativity: Massless particles and photons

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SUMMARY

The discussion centers on the nature of massless particles, specifically photons, and their relationship with the speed of light. Participants clarify that massless particles, such as photons, always travel at the speed of light and do not "become" massless when reaching this velocity. The conversation also addresses misconceptions about mass, emphasizing that photons are massless and lighter than electrons, which have mass. The importance of understanding relativistic mass versus invariant mass is highlighted, with references to the Standard Model of particle physics.

PREREQUISITES
  • Understanding of special relativity and its implications on mass and velocity
  • Familiarity with the concept of photons and their role in light
  • Knowledge of relativistic mass versus invariant mass
  • Basic principles of the Standard Model of particle physics
NEXT STEPS
  • Study the implications of Einstein's theory of special relativity on mass and energy
  • Learn about the properties of photons and their role in electromagnetic radiation
  • Explore the differences between relativistic mass and invariant mass in physics
  • Review the Standard Model of particle physics and its components
USEFUL FOR

Physics students, educators, and anyone interested in understanding the fundamental principles of mass and light in the context of modern physics.

sunmoon
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I f a particle starts moving with the velocity of light it becomes massless.But practically a massless particle has no existence.Again one of the main constituents of light is photon,then is it a massless particle?But I know electron has the least mass in this world and photon is heavier than it.So I am totally confused.
 
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sunmoon said:
I f a particle starts moving with the velocity of light it becomes massless.
It does not.
Particles are either massless, then they always travel at the speed of light, or they are not, then they never do that.
sunmoon said:
But practically a massless particle has no existence.
"Existence" can have philosophical issues, but I think light clearly exists.
sunmoon said:
Again one of the main constituents of light is photon
It is not a constituent. Light can be described with the concept of photons.
sunmoon said:
But I know electron has the least mass in this world
It does not. Neutrinos are lighter. And massless particles are even lighter of course, this includes the photon.
 
sunmoon said:
I f a particle starts moving with the velocity of light it becomes massless.But practically a massless particle has no existence.Again one of the main constituents of light is photon,then is it a massless particle?But I know electron has the least mass in this world and photon is heavier than it.So I am totally confused.

Hi there you have miss understood the equation if a particle travell with speed of light then its mass would become infinity remember the equation

M'= Mo/(√1- V2/C2)
 
Suraj Nehra said:
Hi there you have miss understood the equation if a particle travell with speed of light then its mass would become infinity remember the equation

That is still misleading... Keep in mind that no massive particle can travel with the speed of light...
If you take the limit of the velocity going to c, then you have that the relativistic mass (M' you wrote) goes to infinity, and not the rest (invariant) mass, which we call the mass of a particle.
The relativistic mass is more like the total energy of your particle (contains also the kinetic energy) and that's why the energy is written as E= m_0 \gamma (= m_{rel}).
 
sunmoon said:
I f a particle starts moving with the velocity of light it becomes massless.

You have an error in cause-and-effect here. A particle doesn't become massless when it "starts moving with the velocity of light". It is either massless, or it isn't! If it is massless, then it will move at c. It doesn't become massless when it reaches c.

But practically a massless particle has no existence.

Says who? What natural law are you using here to claim that there are no massless particle, especially when the Standard Model of elementary particle says that there is? Be very careful, on this forum, about espousing your personal beliefs, especially when it is glaringly wrong! Read the PF Rules!

Again one of the main constituents of light is photon,then is it a massless particle?

It is not the "main constituents", it is the ONLY constituent! Light is not made up of anything else.

But I know electron has the least mass in this world and photon is heavier than it.So I am totally confused.

Where did you get that a photon is "heavier" than an electron? It is difficult to answer your question when you are already asking us to explain it based on your faulty understanding. A photon is NOT heavier than an electron, as far as having a mass is concerned. A photon is massless. Period!

Maybe you need to start reexamining one conjecture at a time! Every single sentence that you posted here is faulty! Start from the beginning, and you might learn something without asking if you start reading our FAQ first, because I have a strong feeling a lot of your wrong understanding can be corrected by at least a couple of our FAQs.

Zz.
 
ZapperZ said:
Maybe you need to start reexamining one conjecture at a time! Every single sentence that you posted here is faulty! Start from the beginning, and you might learn something without asking if you start reading our FAQ first, because I have a strong feeling a lot of your wrong understanding can be corrected by at least a couple of our FAQs.

Says the person who have contributed in writing many parts of those FAQs o0) I can feel you there...
 

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