13k views

Could any object have zero mass? [duplicate]

Energy and mass are interrelated. As everything has energy could any object be massless? For example a photon is a packet of energy but still it is considered to be a massless particle. Why is it so?
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1 vote
22k views

Is a photon really massless? [duplicate]

If a photon travels at a speed of light and its massless then it must have no energy but this is not the case as we see in photo electric effect. Also help me to know what are photons made of, how are ...
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2k views

Do photons have mass? [duplicate]

As a student in a highschool physics class, my teacher has repeatedly told me that photons are massless. Yet, I have also heard from other sources that photons have momentum. If photons were to have ...
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807 views

Does light have mass or not? [duplicate]

We know light is made of photons and so it should not have mass, but light is a form of energy (light has energy) and has velocity ($c$), so according to $E=mc^2$, light should have mass... So what is ...
1 vote
11k views

Do Waves have mass? [duplicate]

Do any form of electromagnetic waves like visible light have mass? It is known that all electromagnetic waves have energy. According to Einstein's $$E^2=p^2c^2 + m^2c^4$$ formula, the energy of a ...
7k views

What is the mass of a photon moving at the speed of light? [duplicate]

What is the mass of a photon moving at the speed of light? And if it does not have mass, how is it affected by gravity? Also why does Einstein's general relativity support that a gravitational wave ...
1 vote
2k views

Photons have no mass. So, why does $E = pc$ hold? [duplicate]

It's a somewhat theoretical question. In special relativity, The energy of a photon is given by $E = pc$. But, my argument is that, since photons have no mass, how can they have a momentum $p$? The ...
3k views

Why are two photons created in annihilation? [duplicate]

My textbook says it is because momentum has to be conserved but I don't see how photons can have momentum since they have zero mass (according to my book).
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1k views

Why does a photon have momentum and no mass, yet $p=mv$? [duplicate]

Okay so according to my high-school knowledge I know about inertia and momentum. Now I have a question regarding the photon which my teachers say that is to be learnt in higher classes(and thus not ...
377 views

How to get the accurate relativistic momentum form for photons? [duplicate]

I have studied from Griffiths, the relativistic form of momentum is $$p = \frac{1}{\sqrt{1-\frac{v^2}{c^2}}} m_0v$$ Now when I evaluate the momentum for photon, I just insert $v=c$ and $m_0=0$ and I ...
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502 views

What does momentum of Photons mean? [duplicate]

I have already checked out Can a force stop a Photon since Photons have momentum and What does momentum mean when talking about massless particles?, but that didn't answer my query. I already know ...
521 views

If photons don't have mass, how can they accelerate objects? [duplicate]

As far as I know photons don't have mass but they do have momentum ($p=mv$). Scientists say that if we put a shiny (reflective) shield of large radius in the vacuum of space, then light from sun will ...
1 vote
281 views

Why does photon emit a frequency when its rest mass is zero? [duplicate]

This one really boggles my mind. In the equation $E=mc^2$ and $E=hv$, we can equate $hv=mc^2$. Then, $v/m=c^2/h=k$ (constant) Therefore, $v=k.m$ So, $v$ is directly proportional to m. Lets see the ...
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585 views

De Broglie Wavelength of light [duplicate]

The De Broglie Wavelength is the very evidence of dual nature of particles ( specially photons). But if we use the equation lamda =h/mv, and then put the values of the rest mass of photon (=0) or the ...
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The change in speed of a photon with respect to time is 0 as photons travel at $c$ forever. If no change in speed exists, how can photons have momentum and acceleration? I guess they don't work like ...