Light into matter

[rutineli]

How can light be turned into matter given the right conditions?

[Rev. Green]

Light can spontaneously transform into matter provide that the energy of the photons is not less than the energy equivalent of the mass of the matter formed.

[ChuckFickens]

I think they might mean light turning into matter by shining it into a Bose-Einstein condensate

http://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate

[Pyrrho]

m = e/(c^2) ?

[jake-the-peg]

Perhaps I can flesh out the Rev's comments

Energy and matter are interchangable but the exchange rate is quite steep.

You can't change a whole lot of photons into an electron the energy of a single
photon must be enough to create the new particle.

As mentioned above you need to use E=mc² but you also need the less well known
E=hf where H is planCks constant and f is the frequency.

so hf=mc² or f=mc²/h

h=6.6 × 10-34 m2 kg / s
An electron has a mass of 9.1 × 10-31 kilograms
and c is famously about 3 x 10 ^8 m/s

plug that all in and to get an electron you need a frequency
of 1.25x 10 ^20Hz or 2.4 x10-3 nm in wavelength which is
well in the gamma rays section of the electromagnetic spectrum.

So if you mean visible light, well you can't really it has to be much more energetic.

(Caution for the experts - it is looking extremely likely that the neutrino has a very
tiny mass if that is the case then some of the above assumptions above are off
in this particular case)

[Graham-W]

Photosynthesis. Light from the sun can be turned into a tree or other vegetable matter by photosynthesis. Easy.

[Rev. Green]

Good reply from jake. May I clarify that a gamma-ray can't make just an electron, because that would create a nett electric charge; it must also create something with a neutralising positive charge, a positron for example, so at least double the energy described by jake is needed.

[jake-the-peg]

This is true and it's not just charge that has to balance, there are other things
like hadron number, spin etc.

One reason why matter is often created in pairs

http://en.wikipedia.org/wiki/Pair_production

[RATT23]

Let's see..light is only a transfer of energy....as fire can only release energy.Without MASS there is no light...there is no energy....without matter(or mass) there is no fire.E =M (C x C ).Therfore matter gives life to light, not the other way around.

[Pyrrho]

Nice one Graham :-)