Massless particle "Photon"


It all depends on what you call mass. Mass, as it appears in classical non relativistic case is the measure of material that is contained in the particle. That is one aspect. Mass is the one which appears the force acceleration equation. Larger the mass, lesser the acceleration for the same force. Mass is the one which decides gravitational attraction between two particles at a given distance.

Generally, we take our definition of mass from Force-acceleration relations. This mass is also called Rest mass. Please note that this mass does not change as the particle gains speed.  Very interestingly, the material can be converted into energy. Once that happens material disappears and the mass is lost. The relation is E = mc^2. 

People also define mass from this relation E = mc^2. The energy of a particle is E, its "so called" mass is E/c^2. This is very different from the mass that we know from force-acceleration relations. The name given is relativistic mass. In fact, we do not gain much from this definition and its use is gradually decreasing. You really don't need a new word. Energy serves the purpose and energy and relativistic mass differs by just a constant. I will use mass to mean the one that appears in dynamics equations which is the same as Rest Mass. I even drop the adjective "Rest" as for me a particle has only one mass, whether it moves or not. 

Photon has energy but no mass. If you still wish you can say it has relativistic mass E/c^2 but that has nothing useful. You are only adding a new word for energy.

                                                     #Ankistar
 

 

 

Comments

Post a Comment

Popular posts from this blog

What You Observe Depends On How You Observe It.

Image
Suppose you lose your baseball in the woods, and you and your friend decide to look for it. You know that either you will find it, or your friend will (or it will remain lost). Assuming the ball hasn’t been damaged, it won’t be the case that you and your friend each find half of the ball, or that you both find the ball in different locations. There is only one ball, and it has an exact location, even if you don’t know where it is. It can only be found once, and only by one of you. A wave behaves differently, however. Suppose the ball is dropped into the center of a pond, and you and your friend stand on the shore to look for the wave. You can be on one side of the pond, your friend on the other side, and you can both see the wave wash upon the shore. You can even both see the wave wash ashore at the same time, because part of the wave is near you, while another part is near your friend. This is a fundamental difference between particles and waves. Particles are local, with a
Read more

Neutron Star

Image
In 1932, the neutron was discovered. As mentioned above, two years later, Walter Baade and Fritz Zwicky at the California Institute of Technology hypothesized stars consisting essentially of neutrons. The idea was that if one compresses a star to a density of 10^14 g cm^-3-the density of the nuclei of atoms we are familiar with then the repulsive force between the neutrons. practically touching one another. would prevent any further compression, and the star will be stable. It is just like packing a football with ball bearings; when the ball is jam-packed. it will be quite incompressible. This hypothesis led physicists to the conclusion that even stars more massive than 1.4M ☉   could find ultimate peace. not as white dwarfs but as neutron stars. A density of 10^14 g cm^-3 implies that such stars would be incredibly small, with a radius of mere 10 kilometres! So it appeared that all stars will find peace after all, either as white dwarfs or neutron stars, but this turned out to
Read more

Chandrayaan 2

Image
Chandrayaan-2, India’s second mission to the moon, will comprise an orbiter, a lander named Vikram [after the father of Indian space programme Vikram Sarabhai], and a rover.   It was supposed to be launched on  15 July 2019 at 2:51 IST (14 July 2019 21:21 UTC) but was called off due to a technical snag noticed while filling the cryogenic engine of the rocket with helium   about one hour before launch.  So  the mission was postponed. The landing site for the Chandrayaan-2 rover is expected to be between the two craters Manzinus C and Simpelius N near the southern pole of the moon. The orbiter will go around the moon at an altitude of 100 km, acting as a communication relay between the lander/rover and Earth. The far side of the moon can never be in direct line-of-sight with Earth, proving direct radio communication impossible, which is why the orbiter is needed. It will carry five instruments: A radar that will probe a few metres below the surface to detect water ic
Read more