Question

I know that in particle collider Kinetic energy of the particle is converted into mass (new particles and antiparticles). But can we convert light energy into mass. I know from conservation of mass-energy, theoretically it is possible. But can we do it practically in laboratory?

Can we have a massless particle at rest?
it sounds weird, no mass no "kinetic energy". means no energy at all, but what about potential energy? can it have potential energy in that case, so that i can say it have some energy and hence it exist.
just a curiosity.

Answer 1

Yes. If you bombard deuterium with gamma rays you can distintigrate the deuterium into a proton and a neutron. ie\[H ^{2} + \gamma \rightarrow p +n\] this is called photo desintegration. and has been done for decades. the gamma ray needs to have an energy of 2.22 MeV for this reaction to occur. The photon is absorbed by the deuterium and the results, the proton and the neutron have a combined mass greater than the deuterium.

Massless particles only travel (exist}at the speed of light. no rest for the weightess!!

Answer 2

any way combined mass of proton and neutron will be more than deuterium, because of binding energy. Right?

Answer 3

yes, this binding energy would have been released when a proton and neutron come together to form deuterium, corresponding to the mass difference

Answer 4

Another example (and perhaps more dramatic) of conversion of the energy of a photon to mass is called pair production in which a gamma ray in the presence of a heavy nucleus is spontaneously converted to an electron positron pair. The minimum energy of the gamma ray is the rest masses of the pair ie. 1.022 MeV.

Answer 5

ok, i got it thanks..