mannzzu

do you mean to say photons vibrate at c speed over a very small range? due to which light appears to slow down! then normally photons can interact with atmosphere which has to slow down light in earth's atmosphere. does it happen so? if yes then how come expt to calculate speed of light be accurate?

by vinay"The momentum without mass. And, how does 'energy' travel through 'vacuum'?"

vacuum is set of particles which have all properties like charge, spin,field etc>but it so happens that they cancel out!! (funny!isn't it? i don't know why?)

so they can travel in vacuum

The momentum without mass. And, how does 'energy' travel through 'vacuum'?

what do you feel vaccum is here

yeah if both magnets are exactly similar then strength should not increase acc to my expectation!! because joining increases only the path of magnetic field in the magnet the field from one just takes longer path to other face of another magnet.(here we do need to consider the fields as magneton's instead of imaginary lines)

Merged post follows:

yeah if both magnets are exactly similar then strength should not increase acc to my expectation!! because joining increases only the path of magnetic field in the magnet the field from one just takes longer path to other face of another magnet.(here we do need to consider the fields as magneton's instead of imaginary lines)

how is the assumption zero rest mass accepted for photon?and not for an e-!! both are particles they have relative masses during motion and also both have energy during motion. while e- rest mass is not zero!photon's mass is zero. we also know set of photons can be converted into particles having rest mass,can we convert a single photon(energy) to mass by bringing into rest? if mass is found then it contradicts the assumption!! it will be a paradox!

also the mass of an electron is approximately 9.109×10−31(rest mass) kilogram or 5.489×10−4 atomic mass unit. On the basis of Einstein's principle of mass–energy equivalence, this mass corresponds to a rest energy of 0.511 MeV.

now why not photon(energy) in motion is not having rest energy?

The medium is the material that a wave travels through. For example, when you flick the end of a rope, a wave travels down it. The rope is the medium. No part of the rope is itself traveling down itself. Light is a wave that travels through space, that does not require any medium through which to travel.

what does vacuum(which is considered empty (empty medium)) in this context referring to classical or quantum theory?

acc to classical vacuum means no particle or no mass or energy is present(with no properties)

but acc to quantum as i found in wiki "The vacuum has, implicitly, all of the properties that a particle may have: spin, or polarization in the case of light, energy, and so on. On average, all of these properties cancel out: the vacuum is, after all, "empty" in this sense".

now which case are we considering.

Any bound system is going to have a minimum energy. A free electron could come arbitrarily close to zero kinetic energy.

but 0 kinetic energy is never possible for an e- in an atom!! isn't it?

Merged post follows:

The E&M fields oscillate at some frequency. However, unlike classical waves, the energy of the system is quantized and it requires no medium in which to propagate. So there is an amplitude of the fields, and there is an intensity which is proportional to the number of these quantized vibrational modes, which we call photons.

what do you mean by no medium? no particles in medium?

if photon is considered particle during motion why don't we consider of it bouncing back after giving some energy!! why do we only consider absorption and re emission

if rest mass of photon is zero!! when photon collides with a surface it will lose some energy satisfied by E2-E1 of metal. but at this time during collision photon comes to momentary rest(by some micro seconds)!!!!! does this mean at this time its mass is zero?? if so when it continues its motion where does it regain energy:rolleyes:

conservation is not violated!! we can assume the string is in closed system where in which it loses energy and absorbs the same and the cycle continues!! only question is abt the initial energy!! where does it gain it?????

how come the zero mass at rest gains mass and energy! if it gains energy something has to lose energy

there exists zero point energy which is present at any temperature.hence e- energy is never zero.also any mass has energy!! mass cannot be converted into energy!but can be moved i.e when there's energy its nothing but mass.quantity of enrgy in mass.e- does not fall because it has charge which is always present at all temperature.hence mag field and it still spins..